Re: Heat Treatment Superfluous in Microbial Remediation

[Guest guest]

There is a good paper at the URL below on the porosity of wood frame structures.Fungal spore transport through a building structure.

Airaksinen M., Kurnitski J., Pasanen P. and Seppänen O.

http://lib.tkk.fi/Diss/2003/isbn9512267756/article6.pdfThe paper is part of a doctoral dissertation at:

http://lib.tkk.fi/Diss/2003/isbn9512267756/I think that it explains this issue very well. Basically, the smaller a particle is, the better a chance it has of being able to penetrate throghout a building. The smallest particles are also the most respirable.

Hopefully will answer as well, but I cannot just sit back and let this continue.

In general, all spaces in normal housing are connected. There is some wonderful work available through US researchers and practitioners (most present at the Affordable Comfort conference(s)) that provides both techniques on how to measure and provide data on the leakage between spaces within a building and to the outside, often by a circuitous route. I used to be the custodian of much of the Canadian work on airtightness, but that was almost a decade ago now and the best work now comes from the above persons. In the database I had there was a 1300:1 variability between the loosest exterior tightness and the tightest. It is very difficult to make definitive statements about something with such a range, but even the tightest had significant leakage

Buildings are leaky! That has been the truth in most buildings and still is in most buildings.

In Canada we now have National Building Code requirements for airtightness features, but the buildings are still quite leaky, on the whole (partly because some paths are not covered in the code and partly because builders do not build to the code). In the US there is a great resistance to codifying an air barrier requirement and many builders still think that a vapor retarder is an air barrier (totally different functions, different driving forces and different components).

Since we build with wet wood )steel studs are purposefully perforated) and the structures are flexible, over time previously tight sections get air leaky. this has been documented by many. Very tight construction may only get slightly leakier, if several air barrier layers are used, but most houses and other small buildings start leaky and get leakier. When pressure differences change, in sign and magnitude, air transport though cavities changes as well. This is a simple reality. I tell my sensitive clients that there is no such thing as a good leak in a house once they have a good HRV in place, balanced and running. If there is mold in the cavities that is especially true. Maybe we should be doing cavity tightness tests after we think we have a restored structure that used to have visible surface mold, but now just has hard-to-see mold within cavities (especially between structural elements, between still-drying components).

Jim H. White System Science Consulting systemsa@...

Re: Re: Heat Treatment Superfluous in Microbial Remediation

[Guest guest]

Thanks, Pete.

Steve

[Guest guest]

Hey, " Quack " :

great resource -- thank you!!

Wane

> >

> >

> >

> >

> >

> > Here's another example ...

> >

> > In Florida where I live and many other areas the wall cavities are

> > connected to the attic space. In newer homes they try to seal

the wall top

> > plates but they never really seal them well. The attics are

vented.

> > Whenever there is a wind, the attic space or part of it gets

pressurized

> > and pushes the mold spores and/or dead mold and/or microfragments

along with

> > toxins out of the walls and into the living space thru unsealed

base boards,

> > electrical outlets etc.

> >

> > People sensitive to mold toxins get sick. That's why killing the

mold and

> > leaving it in a wall along with its toxins is not the proper way

to

> > remediate.

> >

> > Rosen, Ph.D.

> > Re: Re: Heat Treatment Superfluous in

Microbial

> > Remediation

> >

> >

> >

>

[Guest guest]

One of my jobs is to inspect homes during construction for builders. I've inspected over 1000 homes during construction. Once one has some practical experience you know that there was never a wall cavity built that was not connected to an attic directly above it.

So why haven't you advised them to run a bead of caulk on the top plate when installing sheetrock and sheathing? Something sounds odd about this. If the builder has hired you to consult for him/her about preventing or remediating mold problems in new construction, why hasn't he/she learned how by the first, say, 100 homes? Or even three homes?

Do you issue the builder a "Clearance Certificate" for each one?

Nice gig if you can get it, I guess. Congrats on that.

Steve Temes

[Guest guest]

Jim,

Thanks for your input based on job site experience that walls are connected. Of course they are. Just because somone may read that walls and attics should not be connected does not make it so.

One of my jobs is to inspect homes during construction for builders. I've inspected over 1000 homes during construction. Once one has some practical experience you know that there was never a wall cavity built that was not connected to an attic directly above it.

Re: Re: Heat Treatment Superfluous in Microbial Remediation

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[Guest guest]

Steve,

It is not so simple as running a bead of caulk otherwise that would get done.

When the plumber runs the toilet stack up thru the metal top plate and then up thru the roof they leave a big jagged hole in the sheet metal top plate. They never patch this. It is a big jagged hole.

Now the electrical is different. These wires are narrow and they fit thru the special holes in the top place made for such wires. The electrical contractors just foam around the wires and they are done. You cannot just foam around the jagged big holes around the toilet stacks.

When the AC contractors run the insulated coolant lines up thru the sheet metal top plate they leave big jagged holes like the plumber. This is very hard to patch.

Also, there are some complex corners and areas involving drop ceilings and such that are not designed to be easily made air tight.

I have tried to get the builders to seal all these openings but since that is hard to do no one wants to spend the money. Unlike water damaged drywall, not sealing around the stacks and coolant lines is not a construction defect. So they want us to focus on water damaged drywall and air leaks around air handler returns that could cause moisture and mold in the AC system. We also focus on penetrations in the exterior that could result in water intrusion and mold.

Rosen

Re: Re: Heat Treatment Superfluous in Microbial Remediation

In a message dated 11/30/2006 1:10:47 PM Eastern Standard Time, garyrosen72652@ yahoo.com writes:

One of my jobs is to inspect homes during construction for builders. I've inspected over 1000 homes during construction. Once one has some practical experience you know that there was never a wall cavity built that was not connected to an attic directly above it. So why haven't you advised them to run a bead of caulk on the top plate when installing sheetrock and sheathing? Something sounds odd about this. If the builder has hired you to consult for him/her about preventing or remediating mold problems in new construction, why hasn't he/she learned how by the first, say, 100 homes? Or even three homes?Do you issue the builder a "Clearance Certificate" for each one?Nice gig if you can get it, I guess. Congrats

on that.Steve Temes

Everyone is raving about the all-new Yahoo! Mail beta.

[Guest guest]

I forgot to answer about Clearance Certificate. Yes I do. But I sample each home first and only will give the certificate if the unit has been under the inspection program from the start. I have a $5M E & O policy. I mostly do mold loss preventation programs high rise buildings in S Fla and Las Vegas.

It is good business if you can get it, but there are many competitors that have very cursory programs and lower pricing that get the bulk of this type of work. These companies are already doing the safety programs and other progams for the builders and just add Mold to the list.

If a builder had a water loss prior to C.O. and did not remove the mold, only killed it with heat or fogging the walls cavities or whatever ... they could be in a bad legal situation. They could be accused of just covering up the problem and delivering an unsafe building with toxins inside the wall cavities. If some rich guy got sick due to mold, the builder could never prove that it was new mold and not mold that they left in the walls.

Because builders have a lot of money, attorneys go after them and they must do things right. I am an expert on a similar case againsts one of the top three national builders. This is not just theory.

Rosen

Re: Re: Heat Treatment Superfluous in Microbial Remediation

In a message dated 11/30/2006 1:10:47 PM Eastern Standard Time, garyrosen72652@ yahoo.com writes:

One of my jobs is to inspect homes during construction for builders. I've inspected over 1000 homes during construction. Once one has some practical experience you know that there was never a wall cavity built that was not connected to an attic directly above it. So why haven't you advised them to run a bead of caulk on the top plate when installing sheetrock and sheathing? Something sounds odd about this. If the builder has hired you to consult for him/her about preventing or remediating mold problems in new construction, why hasn't he/she learned how by the first, say, 100 homes? Or even three homes?Do you issue the builder a "Clearance Certificate" for each one?Nice gig if you can get it, I guess. Congrats

on that.Steve Temes

Everyone is raving about the all-new Yahoo! Mail beta.

[Guest guest]

Steve,

This has nothing to do with heat treatment, but I was wondering about

your comment to run a bead of caulk along the top wall plate before

installing sheetrock.

Do you think that this might cause the structure to become overly tight

by restricting a pathway for the building to breathe? I know that

climate,

etc. will all come into play, but in my experience, residential structures

for the most part still rely on leakage to provide fresh air to the living

space. There are exceptions such as CA where, if I'm correct, a certain

air exchange rate has been mandated by law or code and is

accomplished through the HVAC system.

I could be misunderstanding the direction of this thread, as I have not

been keeping up with it and have come into it in the middle here, but

without forced ventilation, it seems to me that the airflow within a

residential structure, during the heating season at least, and during the

warmest part of the day during average spring and fall days when the

HVAC system isnt' operating, would be to supply make-up air to the attic

exhaust, natural or mechanical, through internal leakage from the lower

floors.

I've seen this many times when there is inadequate exhaust in the attic

and the warm moist air from the living spaces causes considerable

condensation and resultant microbial growth on attic (interior) roof

sheathing and rafters, particularly on the north side. It seems logical

to

me that restricting the abiliity of the exterior (perimeter) wall cavities

to

rise to the attic to be exhausted (to breathe) would result in

condensation in these cavities, thereby promoting microbial growith.

What are your thoughts on how sealing the top plate may impact the

overall natural ventilation of a residential building, particularly in a

cold

climate during the heating season?

Thanks in advance for your thoughts on this, and for anyone else who

cares to chime in on this question.

Cheers,

Chuck Reaney

---------------------------------

So why haven't you advised them to run a bead of caulk on the top

plate when installing sheetrock and sheathing? Something sounds odd

about this. If the builder has hired you to consult for him/her about

preventing or remediating mold problems in new construction, why

hasn't he/she learned how by the first, say, 100 homes? Or even three

homes?

Do you issue the builder a " Clearance Certificate " for each one?

Nice gig if you can get it, I guess. Congrats on that.

Steve Temes

[Guest guest]

Chuck

Once a decent mechanical ventilation system is installed and running there is no advantage (and many disadvantages) to cracks as a source of ventilation air.

By the way, leaky houses often have very poor ventilation, at least in some rooms.

Jim H. White SSC

Re: Re: Heat Treatment Superfluous in Microbial Remediation

Steve,This has nothing to do with heat treatment, but I was wondering about your comment to run a bead of caulk along the top wall plate before installing sheetrock.Do you think that this might cause the structure to become overly tight by restricting a pathway for the building to breathe? I know thatclimate, etc. will all come into play, but in my experience, residential structuresfor the most part still rely on leakage to provide fresh air to the livingspace. There are exceptions such as CA where, if I'm correct, a certainair exchange rate has been mandated by law or code and is accomplished through the HVAC system.I could be misunderstanding the direction of this thread, as I have not been keeping up with it and have come into it in the middle here, but without forced ventilation, it seems to me that the airflow within a residential structure, during the heating season at least, and during thewarmest part of the day during average spring and fall days when the HVAC system isnt' operating, would be to supply make-up air to the atticexhaust, natural or mechanical, through internal leakage from the lower floors.I've seen this many times when there is inadequate exhaust in the attic and the warm moist air from the living spaces causes considerable condensation and resultant microbial growth on attic (interior) roof sheathing and rafters, particularly on the north side. It seems logicalto me that restricting the abiliity of the exterior (perimeter) wall cavitiesto rise to the attic to be exhausted (to breathe) would result in condensation in these cavities, thereby promoting microbial growith.What are your thoughts on how sealing the top plate may impact the overall natural ventilation of a residential building, particularly in acold climate during the heating season?Thanks in advance for your thoughts on this, and for anyone else who cares to chime in on this question.Cheers,Chuck Reaney---------------------------------On 30 Nov 2006 at 15:15, AirwaysEnvcs wrote:So why haven't you advised them to run a bead of caulk on the topplate when installing sheetrock and sheathing? Something sounds oddabout this. If the builder has hired you to consult for him/her aboutpreventing or remediating mold problems in new construction, whyhasn't he/she learned how by the first, say, 100 homes? Or even threehomes?Do you issue the builder a "Clearance Certificate" for each one?Nice gig if you can get it, I guess. Congrats on that.Steve Temes

[Guest guest]

Jim & ,

Thank you for your thoughtful and quite correct input. I probably wasn't

clear in my post. I realize that mechanically assisted ventilation has

many advantages and is preferable to " natural leakage " ventilation, but

I don't think that all builders are currently utilizing mechanically assisted

ventilation.

Therefore, my questions and comments about sealing the top wall

plate and associated elevated moisture/microbial problems apply to

residential structures without mechanically assisted ventilation.

Chuck

To: <iequality >

Date sent: Fri, 1 Dec 2006 11:30:59 -0500

Subject: Re: Re: Heat Treatment Superfluous in Microbial

Remediation

Send reply to: iequality

Chuck

Once a decent mechanical ventilation system is installed and running

there is no advantage (and many disadvantages) to cracks as a source

of ventilation air.

By the way, leaky houses often have very poor ventilation, at least in

some rooms. Jim H. White SSC

Re: Re: Heat Treatment Superfluous in Microbial

Remediation

Steve,

This has nothing to do with heat treatment, but I was wondering

about your comment to run a bead of caulk along the top wall plate

before installing sheetrock.

Do you think that this might cause the structure to become overly

tight by restricting a pathway for the building to breathe? I know

that climate, etc. will all come into play, but in my experience,

residential structures for the most part still rely on leakage to

provide fresh air to the living space. There are exceptions such as

CA where, if I'm correct, a certain air exchange rate has been

mandated by law or code and is accomplished through the HVAC

system.

I could be misunderstanding the direction of this thread, as I have

not been keeping up with it and have come into it in the middle

here, but without forced ventilation, it seems to me that the

airflow within a residential structure, during the heating season at

least, and during the warmest part of the day during average spring

and fall days when the HVAC system isnt' operating, would be to

supply make-up air to the attic exhaust, natural or mechanical,

through internal leakage from the lower floors.

I've seen this many times when there is inadequate exhaust in the

attic and the warm moist air from the living spaces causes

considerable condensation and resultant microbial growth on attic

(interior) roof sheathing and rafters, particularly on the north

side. It seems logical to me that restricting the abiliity of the

exterior (perimeter) wall cavities to rise to the attic to be

exhausted (to breathe) would result in condensation in these

cavities, thereby promoting microbial growith.

What are your thoughts on how sealing the top plate may impact the

overall natural ventilation of a residential building, particularly

in a cold climate during the heating season?

Thanks in advance for your thoughts on this, and for anyone else who

cares to chime in on this question.

Cheers,

Chuck Reaney

---------------------------------

So why haven't you advised them to run a bead of caulk on the top

plate when installing sheetrock and sheathing? Something sounds

odd

about this. If the builder has hired you to consult for him/her

about preventing or remediating mold problems in new construction,

why hasn't he/she learned how by the first, say, 100 homes? Or even

three homes?

Do you issue the builder a " Clearance Certificate " for each one?

Nice gig if you can get it, I guess. Congrats on that.

Steve Temes

[Guest guest]

,

Around here, the electricians utilize the same method as the plumbers. They grab the dullest bit in the box and shred a hole into the framing members. A lot of times, they will even make several holes in an area where they only end up running one wire through.

I'm curious as to why you think big and/or jagged holes can't be easily and inexpensively filled with foam. I sealed every joint and penetration (including complex corners, drop ceilings, and around vent stacks) in my 2340 sq ft attic in about two hours with about $100 worth of expanding foam sealant. Would have been even cheaper if I was buying the foam at wholesale instead of retail prices. Also would have been cheaper if I'd kept the foam on the gaps and cracks instead of getting so much on my hands and pants! Big holes that the plumber had made and then didn't use were filled by first using some duct tape (another use!) across the bottom to hold the foam until it cured enough to stay in place. The foam expands to fill even the most ragged holes and leaves a nice "mushroom" cap out the top.

Wood framing was used in my home (except exterior walls which were ICF), but I don't see why holes in metal framing wouldn't be as easy and inexpensive to fill. I suspect it is more a matter of the builder saving every dollar they can, especially in places that won't show later on. Not that the builders are all to blame. Customers these days demand cheap, so that's what they get.

Similar issue with using a vapor barrier beneath basement slabs. It isn't expensive or difficult to install, just an easy place to cut/save a few hundred dollars.

Curtis Redington, RS

Environmental Quality Specialist

City of Wichita Dept. of Environmental Health

Wichita, KS

-----Original Message-----From: iequality [mailto:iequality ]On Behalf Of gary rosenSent: Thursday, November 30, 2006 3:54 PMTo: iequality Subject: Re: Re: Heat Treatment Superfluous in Microbial Remediation

Steve,

It is not so simple as running a bead of caulk otherwise that would get done.

When the plumber runs the toilet stack up thru the metal top plate and then up thru the roof they leave a big jagged hole in the sheet metal top plate. They never patch this. It is a big jagged hole.

Now the electrical is different. These wires are narrow and they fit thru the special holes in the top place made for such wires. The electrical contractors just foam around the wires and they are done. You cannot just foam around the jagged big holes around the toilet stacks.

When the AC contractors run the insulated coolant lines up thru the sheet metal top plate they leave big jagged holes like the plumber. This is very hard to patch.

Also, there are some complex corners and areas involving drop ceilings and such that are not designed to be easily made air tight.

I have tried to get the builders to seal all these openings but since that is hard to do no one wants to spend the money. Unlike water damaged drywall, not sealing around the stacks and coolant lines is not a construction defect. So they want us to focus on water damaged drywall and air leaks around air handler returns that could cause moisture and mold in the AC system. We also focus on penetrations in the exterior that could result in water intrusion and mold.

Rosen

Re: Re: Heat Treatment Superfluous in Microbial Remediation

In a message dated 11/30/2006 1:10:47 PM Eastern Standard Time, garyrosen72652@ yahoo.com writes:

One of my jobs is to inspect homes during construction for builders. I've inspected over 1000 homes during construction. Once one has some practical experience you know that there was never a wall cavity built that was not connected to an attic directly above it. So why haven't you advised them to run a bead of caulk on the top plate when installing sheetrock and sheathing? Something sounds odd about this. If the builder has hired you to consult for him/her about preventing or remediating mold problems in new construction, why hasn't he/she learned how by the first, say, 100 homes? Or even three homes?Do you issue the builder a "Clearance Certificate" for each one?Nice gig if you can get it, I guess. Congrats on that.Steve Temes

Everyone is raving about the all-new Yahoo! Mail beta.

[Guest guest]

I have tried to get the builders to seal all these openings but since that is hard to do no one wants to spend the money. Unlike water damaged drywall, not sealing around the stacks and coolant lines is not a construction defect. So they want us to focus on water damaged drywall and air leaks around air handler returns that could cause moisture and mold in the AC system. We also focus on penetrations in the exterior that could result in water intrusion and mold.

Rosen

If you substantially sealed each bay/cavity with a continuous bead of glue or caulk leaving an occassional small opening at the top or one side, at least you wouldn't have air FLOW. You would have a cavity with a "dead head" of pressure. This would still be much better than more than one opening in a cavity that would constitute a pathway connecting the conditioned space and the attic or outdoors. I see nothing but benefits to be gained from sealing wall cavities and gasketing electrical receptacle and light switch plates.

Most sheetrock in wood framing is glued and screwed in place anyway. Even the specs for resilient channel (acoustically attenuated) wall construction call for gasketing or caulking of the sheetrock to the metal framing. Wall cavities should be sealed. A sill gasket is important to prevent air from coming in from under the the wall framing. I don't accept that leakage can't be minimized with little effort.

In Florida, especially, I would think that outdoor air leakage into a wall cavity would be something very important to prevent. You don't want that humidity getting inside of an air conditioned wall.

Steve Temes

[Guest guest]

I've seen this many times when there is inadequate exhaust in the attic

and the warm moist air from the living spaces causes considerable

condensation and resultant microbial growth on attic (interior) roof

sheathing and rafters, particularly on the north side. It seems logical

to

me that restricting the abiliity of the exterior (perimeter) wall cavities

to

rise to the attic to be exhausted (to breathe) would result in

condensation in these cavities, thereby promoting microbial growith.

What are your thoughts on how sealing the top plate may impact the

overall natural ventilation of a residential building, particularly in a

cold

climate during the heating season?

Chuck,

I will defer to others, like some or our Canadian list members who have studied the science more formally, for citations of studies and literature references. The heating season is longer up there and more is at stake with regard to energy savings and snowfall issues.

Here's what I know (but anyone correct me if I'm wrong)... The ceiling plane should be intact. This includes top plate penetrations. Recessed light fixtures and pull-down attic stairs can let warm, humid air into the attic in winter. In my experience, over-humidification is usually the major problem in these "north slope" condensation cases rather than inadequate "exhaust" or ventilation (although they are two sides of the same coin). In addition to general condensation on the underside of the roof, when the warm air gets into the attic, it will rise to the peak and melt the snow pack at the top of the roof slope. The water runs down and freezes when it gets to the cold bottom of the slope creating ice damming. I have seen sheets of ice crystals form on the underside of the roof sheathing at the bottom portion of the roof slope where there is an ice pack on top. It can take a while for that ice to melt when it gets thick. Those areas of the roof under the ice stay very cold for a long time causing more condensation (or sublimation) than anywhere else. This creates mold and rot and delamination of plywood sheathing. You don't want warm air leaking into an attic in the winter and you don't want warm, humid air leaking into the walls of an air conditioned house in the summer.

Makeup air for attic ventilation should come from soffit vents (or other intentional attic vent openings), definitely not perimeter wall cavities or leakage from any interior space.

And this excludes the energy cost considerations which are very significant.

Steve Temes

[Guest guest]

That's right. Of course they could fix the holes but in production homes in my experience in my state they do not fix them. It is not part of building code is our state to seal such holes so the builder does not worry about it even though the house would be better built if they did.

Rosen

Re: Re: Heat Treatment Superfluous in Microbial Remediation

In a message dated 11/30/2006 1:10:47 PM Eastern Standard Time, garyrosen72652@ yahoo.com writes:

One of my jobs is to inspect homes during construction for builders. I've inspected over 1000 homes during construction. Once one has some practical experience you know that there was never a wall cavity built that was not connected to an attic directly above it. So why haven't you advised them to run a bead of caulk on the top plate when installing sheetrock and sheathing? Something sounds odd about this. If the builder has hired you to consult for him/her about preventing or remediating mold problems in new construction, why hasn't he/she learned how by the first, say, 100 homes? Or even three homes?Do you issue the builder a "Clearance Certificate" for each one?Nice gig if you can get it, I guess. Congrats

on that.Steve Temes

Everyone is raving about the all-new Yahoo! Mail beta.

__________________________________________________

[Guest guest]

I undertand your point. It makes sense and I don't disagree at all. In Florida it is our custom to caulk the tops of baseboards. This significantly helps stop the air flow from the attic to the house. In many or most other states, they don't caulk to top of the base and that is a huge mistake in my mind.

But there are other areas that leak for instance around electrical outlets. Unless the building is a high rise where they use fire caulking around the electrical outlets, air from the wall cavitiy will get into the house thru the electical plates or around light fixtures in the ceiling; or around most AC vents in the ceiling or walls as these are usually not properly sealed.

I am just stating that these are not sealed in practice. But they should be.

When the house has a non-ducted AC return you have quite a bit of negative pressure pulling stuff out of the walls and ceilings... especially around the air handler closet if it is not well sealed. This is not typically such a problem when the return is ducted (back into the AC unit)

Rosen

Re: Re: Heat Treatment Superfluous in Microbial Remediation

In a message dated 12/1/2006 3:48:18 PM Eastern Standard Time, garyrosen72652@ yahoo.com writes:

I have tried to get the builders to seal all these openings but since that is hard to do no one wants to spend the money. Unlike water damaged drywall, not sealing around the stacks and coolant lines is not a construction defect. So they want us to focus on water damaged drywall and air leaks around air handler returns that could cause moisture and mold in the AC system. We also focus on penetrations in the exterior that could result in water intrusion and mold. RosenIf you substantially sealed each bay/cavity with a continuous bead of glue or caulk leaving an occassional small opening at the top or one side, at least you wouldn't have air FLOW. You would have a cavity with a "dead head" of pressure. This would still be much

better than more than one opening in a cavity that would constitute a pathway connecting the conditioned space and the attic or outdoors. I see nothing but benefits to be gained from sealing wall cavities and gasketing electrical receptacle and light switch plates.Most sheetrock in wood framing is glued and screwed in place anyway. Even the specs for resilient channel (acoustically attenuated) wall construction call for gasketing or caulking of the sheetrock to the metal framing. Wall cavities should be sealed. A sill gasket is important to prevent air from coming in from under the the wall framing. I don't accept that leakage can't be minimized with little effort.In Florida, especially, I would think that outdoor air leakage into a wall cavity would be something very important to prevent. You don't want that humidity getting inside of an air conditioned wall.Steve Temes

Access over 1 million songs - Yahoo! Music Unlimited.

[Guest guest]

Steve,

Thanks for your reply. What you state all makes sense, and as I

indicated the instances of extreme attic roof sheathing and rafter

growth have been due either to inadequate exhaust, and now that I'm

thinking more about it, also blocked or non-existant soffit vents to allow

for the make-up air, or a combination of both. The result was, of

course, the make-up air being drawn from the warm, moist interior air

of the living space, facilitating the problems described.

Sealing the top wall plate makes sense to reduce the transfer of

conditioned interior air to the attic. Ok.

I'm a thick-headed Irishman, so sometimes it takes me a while to think

things through all the way, so here's my next question...

Applying both your explainations and my remembering that the worst

case problems that I described were due to blocked or inadequate

soffit venting, how is the equivalent of adequate soffit venting and

adequate exhaust accomplished in perimeter walls? SOME level of

interior (warm, moist) air must exfiltrate to the perimeter wall cavities,

and with the top plate sealed, would tend to condense on surfaces

within these cavities (particularly on the north side in colder climates).

The reverse is applicable in warm, moist climates such as Florida in

considering asociated air conditioning concerns.

Double pane (insulated) windows are an excellent, simplified example

of this. When these windows are sealed (and filled with a gas with

poor thermal transfer properties (which wall cavities are not), as they

are manufactured, they work well. But if something causes a breach in

the seal, the issues of condensation/frost become quite obvious.

I realize that adequate thermal insulation (fiberglass) would serve to

significantly reduce this, but is the insulation alone adequate in

preventing this scenario, without the walls being completely air-tight (on

both sides), as the insulated, double pane windows are?

Thanks in advance for your consideration of the above points, and any

forthcoming explainations/opinions.

Chuck Reaney, THIE (Thick Headed Irishman Extraordinaire)

------------------------------------

In a message dated 12/1/2006 10:29:07 AM Eastern Standard Time,

creaney@... writes:

> I've seen this many times when there is inadequate exhaust in the

> attic and the warm moist air from the living spaces causes

> considerable condensation and resultant microbial growth on attic

> (interior) roof sheathing and rafters, particularly on the north

> side. It seems logical to me that restricting the abiliity of the

> exterior (perimeter) wall cavities to rise to the attic to be

> exhausted (to breathe) would result in condensation in these

> cavities, thereby promoting microbial growith.

>

> What are your thoughts on how sealing the top plate may impact the

> overall natural ventilation of a residential building, particularly

> in a cold climate during the heating season?

Chuck,

I will defer to others, like some or our Canadian list members who

have studied the science more formally, for citations of studies and

literature references. The heating season is longer up there and more

is at stake with regard to energy savings and snowfall issues.

Here's what I know (but anyone correct me if I'm wrong)... The

ceiling plane should be intact. This includes top plate penetrations.

Recessed light fixtures and pull-down attic stairs can let warm,

humid air into the attic in winter. In my experience,

over-humidification is usually the major problem in these " north

slope " condensation cases rather than inadequate " exhaust " or

ventilation (although they are two sides of the same coin). In

addition to general condensation on the underside of the roof, when

the warm air gets into the attic, it will rise to the peak and melt

the snow pack at the top of the roof slope. The water runs down and

freezes when it gets to the cold bottom of the slope creating ice

damming. I have seen sheets of ice crystals form on the underside of

the roof sheathing at the bottom portion of the roof slope where there

is an ice pack on top. It can take a while for that ice to melt when

it gets thick. Those areas of the roof under the ice stay very cold

for a long time causing more condensation (or sublimation) than

anywhere else. This creates mold and rot and delamination of plywood

sheathing. You don't want warm air leaking into an attic in the

winter and you don't want warm, humid air leaking into the walls of an

air conditioned house in the summer.

Makeup air for attic ventilation should come from soffit vents (or

other intentional attic vent openings), definitely not perimeter wall

cavities or leakage from any interior space.

And this excludes the energy cost considerations which are very

significant.

Steve Temes

[Guest guest]

:

As an FYI, California’s Title 24 Energy Code standards require the sealing that you mention is not being done in Florida.

Also, my opinion of caulk between the sole-plate, or channel, and the slab is.....It leaks. While it may offer an effective seal for the first year or two, a bead of caulk will not last. I prefer a 4in wide, 3/8in thick, poly-cell foam tape. It is quite inexpensive by the 150-ft roll and about the same cost as several tubes of caulk. It offers a much superior seal and it lasts. However, it is a chore to get it installed correctly and keep it positioned when stick framing; metal channel is much easier.. I often use a cheap caulk just to hold the tape in place while we stand wood-framed walls.

--

Geyer, PE, CIH, CSP

President

KERNTEC Industries, Inc.

Bakersfield, California

www.kerntecindustries.com

I undertand your point. It makes sense and I don't disagree at all. In Florida it is our custom to caulk the tops of baseboards. This significantly helps stop the air flow from the attic to the house. In many or most other states, they don't caulk to top of the base and that is a huge mistake in my mind.

But there are other areas that leak for instance around electrical outlets. Unless the building is a high rise where they use fire caulking around the electrical outlets, air from the wall cavitiy will get into the house thru the electical plates or around light fixtures in the ceiling; or around most AC vents in the ceiling or walls as these are usually not properly sealed.

I am just stating that these are not sealed in practice. But they should be.

When the house has a non-ducted AC return you have quite a bit of negative pressure pulling stuff out of the walls and ceilings... especially around the air handler closet if it is not well sealed. This is not typically such a problem when the return is ducted (back into the AC unit)

Rosen

Re: Re: Heat Treatment Superfluous in Microbial Remediation

In a message dated 12/1/2006 3:48:18 PM Eastern Standard Time, garyrosen72652@ yahoo.com writes:

I have tried to get the builders to seal all these openings but since that is hard to do no one wants to spend the money. Unlike water damaged drywall, not sealing around the stacks and coolant lines is not a construction defect. So they want us to focus on water damaged drywall and air leaks around air handler returns that could cause moisture and mold in the AC system. We also focus on penetrations in the exterior that could result in water intrusion and mold.

Rosen

If you substantially sealed each bay/cavity with a continuous bead of glue or caulk leaving an occassional small opening at the top or one side, at least you wouldn't have air FLOW. You would have a cavity with a " dead head " of pressure. This would still be much better than more than one opening in a cavity that would constitute a pathway connecting the conditioned space and the attic or outdoors. I see nothing but benefits to be gained from sealing wall cavities and gasketing electrical receptacle and light switch plates.

Most sheetrock in wood framing is glued and screwed in place anyway. Even the specs for resilient channel (acoustically attenuated) wall construction call for gasketing or caulking of the sheetrock to the metal framing. Wall cavities should be sealed. A sill gasket is important to prevent air from coming in from under the the wall framing. I don't accept that leakage can't be minimized with little effort.

In Florida, especially, I would think that outdoor air leakage into a wall cavity would be something very important to prevent. You don't want that humidity getting inside of an air conditioned wall.

Steve Temes

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