Old House, no insulation, interior plaster removed...what to do? 3

[FreeRangeMonkey]

I am working on an old house in Oakland, CA which was damaged by fire several months ago. I am designing a new roof and will be doing the interior as well. THe problem is, the client demo'ed the interior down to the studs and there is no building wrap between the studs and the siding as one would see in a newer house in CA. There was also no insulation in the walls. We will be completely re-drywalling the interior.

I am trying to figure out the best way to insulate the walls and need to know what to do in terms of vapor and moisture control. Options I am considering include...

1) leave the walls the way they are and use batt, foam or cellulose insulation.

2) paint the interior of the walls/studs with an elastomeric paint such as Henry-BES, then use insulation.

Any ideas?

Primary concerns are that the house breathes, does not pull moisture into the walls and does not cause any damage that can be traced to the remodel.

 

[swBausch]

House wrap is about air infiltration, not moisture. If the current exterior will remain, you won't have opportunity to improve the air-tightness of the exterior by house-wrap.

The only place to apply a water vapor membrane is immediately behind the drywall. That's why fiberglass has the foil or kraft paper; those are vapor barriers.

Painting the interior stud cavities with elastomeric would not be a good idea since it would seal in the water vapor.

 

[FreeRangeMonkey]

Does not house wrap also force any condensation to drip down it so that it does not infiltrate the building envelope any further...the whole thing about heating climates v. cooling climates and where to put the vapor barrier also comes into play here.

So then, what is the best way to seal the house against air drafts without creating a larger problem with water vapor?

 

[swBausch]

Perhaps the best choice of your declared options is to place plastic sheet on the studs, apply drywall, and come back later to blow cellulose into the cavities, with an emphasis on 'packing' the cellulose, to provide draft restriction.

Unless the exterior is to be removed/replaced. In that case you could apply building wrap before the siding.

Fiberglass batting is quite popular, and I use it, but I think it's weakness is effective draft control.

You mentioned foaming the stud cavities. I think it's a nifty idea, but it's not mainstream.

 

[swBausch]

You asked if wrapping would cause condensation. The beauty (and selling point) of wrap is it's ability to stop drafts, but not water vapor migration.

If you want to stop drafts AND water vapor, that's what plastic sheet is good for, but you cannot have plastic sheet between the insulation and the outside conditions.

The junction of insulation and outside condition (winter) is colder than the junction of insulation and living space. So.....if the vapor barrier is at the insulation/outside junction, there is an excellent chance that the warm moist air of the living space will migrate through the insulation, be stopped by the vapor barrier, and accumulate as moisture.

The above behavior can be seen on the windows of your automobile. In winter, the fogging will be inside the auto, when only the heater is running (A/C usage would dehumidify, and screw up the effect) . You may also see fogging of your auto's 'vapor barrier' on a summer evening, if you have the air conditioner sending the chilled air directly onto the windshield. In the summer, the fogging won't be on the inside, it would be on the outside.


I had the experience of growing up in an old house without double-glazing. Nothing like watching ice build up on the inside of a window to understand that air contains moisture. You more 'fortunate' types may have difficulty comprehending the dynamics of vapor barriers.

Also, sleeping in a sleeping bag in winter is another excellent demonstration of water vapor. Inside the bag, everything is fine, the insulation (sleeping bag) is doing it's job. However, as the vapor migrates though the insulation, it passes through colder areas, and may eventually condense, and perhaps freeze. The outside of the sleeping bag may become rigid from the ice.

 

[jrhols]

In california, Sun is a concern. This is best deal with on the first surface with a low emissivity paint like Supertherm. That helps inside the walls because you don't feel the need to put in a low emissivity barrier if the paint is on outside. You should use an elastomeric enhancement like PolyMatRx if any paint you are putting on is the first coat of paint on a surface, a must if on a metal surface. Don't use batting, don't buy any insulation because it is a waste of money. These american corporations are corrupted. Use garbage bags filled with Argon and whatever other material, from old leaves to straw, but be sure to treat it with phosporic acid (a good idea if the walls are bare wood too) so that it won't burn. Apparently that was not already done in the past or there would have been no fire. IT's $25 at Fleet Farm for 5 gal. Ask for Milk house wash. I closed my web page recently because nobody bought from my page, but I did show how R values are being misused. In metric the standard is a thin fiber, but in ECS the standard is a foot of pipe with a foot of area of 1 inch insulation . So, divide Air's conductivity by the quantity 39.37 times 2 pi, and you get metric conductivity K value. K is 1 over R. Anyway, they all lie like fools. Air is R 2.119 maximum. No insulation except argon beats it. Hope I'm not too late to save your project, but I get fed up with being squashed like a bug by dishonesty. Iso-9000, yeah right what a joke. At least I'll say for these corporations, they hire organized people.
Too bad they don't have anything that means something to anybody else!

 

[FreeRangeMonkey]

I am currently still in Design Review on said project, so it is not yet resolved, but I believe that the limitations of the existing walls are dictating that I must leave the walls uninsulated. Glad to hear that it may not be such a problem!

 

[jrhols]

It wouldn't be a problem to use air alone- that is how an attic works, because there is no convection happening due to the size of the air space in an attic. The nearness of the studs in a wall creates convection flowing near the surface, and their velocity begins other currents. Also whenever a steep temperature gradient exists in a gas, depending on the weight of the gas, it is very powerful physics that push the less dense air above the more dense cold air, but moisture reverses this effect putting more moise air higher because it is less dense. You should therefore consider how to limit convection. Argon gas is very heavy compared to air and has twice the conductivity resistance. Under thermal stress that won't stop the insulation effect breaking down, so again bagging it up is the way, small bags are better. I have a post asking where I could buy air bags used in locomotive box car freight trains. These will take the pressure and last long, but may be expensive and certainly harder to find as the train companies don't like losing their stocks. Moisture also doubles the heat transfer at 100 percent saturation of air, and so condensation should be addressed. Water absorbing materials would help. Roofs use air movements vents. A solar heat collector that acts as a venting input/ouput device will take out accumulated moisture and add heat to the walls while being passive in power use. They cost too much but you can buy aluminum cheap sometimes from old pipe.

 

[LFOD]

In the US we normally call K factor U. The inverse of R.
Just as in cold climates insulation keeps heat in, in warm climates it also keep heat out. The two most widely used types of insulation are rigid and fiberglass batt. Each has it's own positive attributes and applications. Don't go with blown-in insulation. In my opinion this stuff is simply one way for someone to get rid of their trash and place it in your walls.
If you use batt insulation use a vapor barrier. The trick is to not allow moisture to develop within it, otherwise it's useless. The location of the dewpoint must not be within the thickness of your insulation. The way to do this is simply by installing a vapor barrier with proper joint preparation, lap and tape, even eletrical boxes. This done the only way for moisture to escape is at the holes in your structure, i.e. windows and doors. Make sure these are good quality and have a thermal break.
You don't want to make a building that is too tight though. Because then too much moisture can remain and condensate on other interior surfaces. Air quality can then also become an issue (mold spores, mildew, etc.) when a regular exchange of air is not taking place.
I wouldn't advise anyone of putting leaves or any other combustible material within the interstitial space of a wall. Check your local or state building code to see what are acceptable materials for insulation.

 

[ERV]

If using batt insulation, and in your situation this is what I would recommend, use the type that is fiberglass encapsulated in plastic (bag like).

Forced air heating/AC will take care of excess moisture accumulation if properly designed. It is of paramount importance to properly design the heating/AC system to keep interior humidity to around 55%. If the dwelling does not have forced air heating/AC, I suggest spending the dollars to install a properly engineered system above all else. A properly designed system can handle excess infiltration, summer or winter. Oakland, CA has relatively mild weather year round, I do not think that it would be important to provide vapor barriers or limit infiltration. Dollars would be wasted that could be spent much more constructively. The key here is human comfort year round and as such make that the goal through research.

I routinely design these systems in existing and new construction, infiltration ranges from extremely tight to almost barn like. Proper design can accomodate ALL conditions.

If you would like more info let me know. I have a wealth of information and knowledge I will share.

 

[Verna]

I would recommend using Icynene insulation. It's breathable and an air barrier. It will expand to fill all the cracks and voids that batt insulation will not get in an old house with irregular stud spacing.

 

[pmkPE]

Check out the following web site for Icynene insulation - they have a very short demo video of the insulation being sprayed on. Very impressive:

http://www.wfionline.com/Icynene Insulation.htm