New Vinyl Siding and Exterior Insulation

Moved to Roofing and Siding forum.

Hi Joe, a confusing issue.
Although you will frequently see foil faced insulation going up under new siding, that doesn't mean it is a good idea. Certainly the extra insulation and the continuous layer from foundation to top plate is outstanding, the problem deals with too many vapor barriers. If your interior walls were built with a plastic vapor barrier or even vinyl wall paper then the wall assembly will not be able to dry to the inside or outside, not good. A non-foil faced rigid might work as they do allow a small amount of moisture to pass. For a better explanation, link below.

Be sure they tape all seams with a foil tape and if a shiplap 4x8 panel is an option they seal better. Although the polyiso has an initial high r-value, it declines over time and check out its r-value vs temperature, it goes down as the insulation gets cold, second link.

http://www.greenbuildingadvisor.com...rmal-mass&utm_campaign=green-building-advisor

http://www.greenbuildingadvisor.com/articles/dept/musings/cold-weather-performance-polyisocyanurate

Bud

#1, You need to figure out your wall make up first to see if the added cost is worth it.
Is it 2 X 4's or 6's?
This is strictly my own opinion.
Adding 2" thick insulation on a retrofit Is going to force them to have to build out all the door and window trim a lot so the siding does not stick out past the trim.
Adding fan fold insulation and using insulated siding would add about an R-5, so if you only have 2 X 4 walls that would give you an R-18 wall which is close to the R-19 to meet modern codes.

joecaption said:

#1, You need to figure out your wall make up first to see if the added cost is worth it.
Is it 2 X 4's or 6's?
This is strictly my own opinion.
Adding 2" thick insulation on a retrofit Is going to force them to have to build out all the door and window trim a lot so the siding does not stick out past the trim.
Adding fan fold insulation and using insulated siding would add about an R-5, so if you only have 2 X 4 walls that would give you an R-18 wall which is close to the R-19 to meet modern codes.

Click to expand...

The contractor showed me what is behind the siding. A few pics...
https://drive.google.com/file/d/0B5yA9OoW_XgJSVFFWDJoc0RsY00/view?usp=sharing
https://drive.google.com/file/d/0B5yA9OoW_XgJbW1hbncwZFlNREk/view?usp=sharing

I am not sure what we have behind the interior walls, though the house was built in 1929, I think.

joetab24 said:

I am not sure what we have behind the interior walls, though the house was built in 1929, I think.

Click to expand...

Do you mean exterior walls? For purposes of discussion an exterior wall has the great outdoors on one side whereas an interior wall has inside living space on both sides.
A house built in 1929 may not have any insulation in the exterior walls unless it was added later. I would start by removing an electrical cover plate on an exterior wall and see if you can tell what insulation you may or may not have in the walls.

"For purposes of discussion an exterior wall has the great outdoors on one side whereas an interior wall has inside living space on both sides."

ok, i see. I was referring to our living room walls as the interior wall. And I was referring to the area outside, covered by the existing siding, as an exterior wall. So I see where I am being confusing. I am talking about two sides of the *same* wall.

If you remove a cover plate on a wall switch or outlet the box inside may have some holes to allow you to see or poke a wire on the other side.

JUST REMEMBER THERE ARE LIVE WIRES IN THERE :vs_bulb:unless you pull a fuse or flip a breaker

I don't see any insulation in there.

I am leaning towards not adding insulation, especially given the potential moisture problems I am reading about when it comes to old houses with foam insulation added on the outside, behind the siding.

If the siding is coming off anyway the walls can be insulated from the outside.
Also a great time to add new outlets, run new wiring, add fire blocking if it's balloon wall constrution, air seal any holes where the wring was run.

If there is no insulation inside the walls, then while the siding is off it would be an easy install to blow in cellulose.

Not sure what articles you are reading that are scaring you away from exterior foam, but it is a common practice and works well. If you provide links we can review what they are saying. Many moisture issues are reduced or eliminated by air sealing and a thick layer of rigid insulation on the outside, caulked and or taped to be air tight, will greatly enhance the performance of those walls. That should also include the insulation inside the wall cavities.

Bud

Hi Bud,

I was reading from these two sources:
http://www.oldhouseonline.com/expert-advice-insulation/
http://bobyapp.com/blog/2009/06/myths-about-insulating-old-house-walls

Like most people, our budget is limited and we have a few jobs that need to be done in addition to the siding. Have been in the house since 07 and our heating and cooling costs have been manageable, so I am not sure how much I want to spend adding insulation, especially if I might possible create moisture issues that do not currently exist. I definitely think our attic could be better insulated. And I know that is something I should address as soon as I can.

Hi Joe,
I read both links and see where you are concerned. However, with the emphasis on following the rules and doing the work correctly, those old houses can certainly be improved. I prefer reading the more science based articles from greenbuildingadvisor.com or buildingsciencecorp.com. I added one below.

In regards to the payback, they energy costs have certainly changed and I see many homes opting to add solar as opposed to insulation.

A key with all improvements is air sealing and paying attention to moisture control. Air sealing is rather easy, the moisture control takes a lot of reading.

One of the best pieces of advice I can offer all home owners is to take advantage of convenient opportunities to make improvements. With the siding off, the improvements discussed are a lot easier.
http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/insulating-stud-cavities-existing-homes

Best
Bud

Thanks, Bud!