Author Topic: Insulating my home  (Read 2732 times)

Photoshow

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Insulating my home
« on: December 16, 2015, 07:32:01 PM »
I have a few questions about insulating as I'm about to put on new siding.

First by way of background, I insulated my attic a while back after MMM wrote the article on doing so. I blew in enough cellulose to bring the attic to about R50 but a contractor talked me out of trying to airseal - I don't recall if he convinced me it wasn't worth it or if I didn't need it. I think I may have made a mistake. Is there a good way to go back and airseal now that all the cellulose is in there?

Second, I have 40 year old brand-name double pane wooden Windows. They work fine so I don't think they're worth replacing but want your opinion.

Lastly, the house is brick front and asbestos shingle siding on the remaining three sides. We're having the three sides redone in vinyl siding. Contractor suggested we put quarter inch high density insulation up on top of the shingles then put the siding over top. I liked the idea from an insulation perspective and asked what we could do to further insulate the walls. He said the new siding will be a nice air seal but the insulation board we're using will provide little r-value. Since the seal is there and since we don't want the sides sticking out too far we shouldn't change the thickness of the insulation. So my questions are this:

1. What can be done now to seal the attic? Is it too late?
2. Should I be considering new windows?
3. I don't want to mis my opportunity to insulate the walls. Should I go with the current plan or should I be considering something else?

TIA
« Last Edit: December 16, 2015, 07:35:21 PM by Photoshow »

bacchi

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Re: Insulating my home
« Reply #1 on: December 16, 2015, 10:46:39 PM »
2) No. Leave the wood windows.

3) Do you have a moisture barrier in the walls? What climate zone are you? Rigid foam insulation of that thickness will cause condensation problems anywhere north of, say, Atlanta. Bad idea.

Photoshow

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Re: Insulating my home
« Reply #2 on: December 17, 2015, 07:17:09 AM »
thanks bacchi! Some follow up...

1) any thoughts on this?

2) thanks, I'll leave the windows as-is.

3) I have no idea what's in the walls; my guess is whatever was code in the early 1970's is what is in my walls (less deterioration). I'm in Maryland. The insulation is going over the asbestos shingle to prevent the cost of removal plus keeping the r-value they bring. This insulation board plus whatever they do to seal (just the standard installation) could cause a condensation issue? So what would you recommend? Tear out shingles, add thicker insulation board, then add siding?

Thanks!

argonaut_astronaut

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Re: Insulating my home
« Reply #3 on: December 17, 2015, 07:56:35 AM »
Responses to your questions:
  • It will be one totally sucky day that will pay off every day after it. Go get a tyvec suit, a respirator, and a 6 cans of fire block spray foam. Seal every ceiling box, follow the tops of the walls and fill any holes drilled for electrical, around plumbing vent pipes, and bathroom fan boxes. Use silicone caulk around chimneys/hot exhaust pipes
  • Windows should be fine. Make sure all the gaskets are in good shape and replace as needed.
  • You need to know if your walls already have a vapor barrier along with how much insulation you currently have. If you already have a vapor barrier then you will be creating a trapped air space between the rigid foam and that barrier that will collect moisture and create mold/rot. Do some more research on vapor barriers and insulation and don't trust that your contractor knows what he/she is doing. Here is a good place to start http://buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

If you want more help it would be good to know the age of your house and locale/climate.
« Last Edit: December 17, 2015, 07:58:36 AM by argonaut_astronaut »

bacchi

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Re: Insulating my home
« Reply #4 on: December 17, 2015, 09:41:04 AM »
1) any thoughts on this?

What argonaut wrote. Or, if it's densely packed, accept that there will be some leakage but it's ~10x better than it was.

Quote
So what would you recommend? Tear out shingles, add thicker insulation board, then add siding?

That depends on what's behind the asbestos. Sheathing, tar paper, just studs? You can always pull off shingles on the top row, blow in cellulose, put on the new siding, and then seal the house interior extremely well. That's probably cheaper than rigid foam, too. In your climate, you'll need very thick rigid foam to stop moisture collection inside the walls.

http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing

Quote from: gba
Thin foam is dangerous...

psinguine

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Re: Insulating my home
« Reply #5 on: December 17, 2015, 01:20:33 PM »
Rigid foam board on the exterior sounds good in theory. It can be damaging in practice. Personally, if I knew there was a vapour barrier on the interior, I would remove the existing siding to free up more thickness and utilize the Roxul Comfortboard product. Very similar to foam board in that it's rigid, but it breathes and remains fire/water resistant. The cost can be prohibitive though.

On the interior, as to air sealing, I would not try to slog around in the cellulose. You will destroy its ability to insulate by conpacting it. At this point your modus operandi should be to:
 - Paint interior of house with a paint intended for air sealing
 - Utilize expanding foam around windows/doors (remove trims for this)
 - Install gaskets behind outlet/switch covers
 - Caulk any and all openings through walls

 I could go on at length, but I think you get the idea. Air sealing is a monumental pain in the ass when the walls are already finished. And anything you do will never be as good as starting with a proper Vapor Barrier would have been.

And if the window units themselves aren't leaking (you would know because they would be fogging between the glass) then don't worry about them. 

Midwest

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Re: Insulating my home
« Reply #6 on: December 17, 2015, 01:28:55 PM »

3) Do you have a moisture barrier in the walls? What climate zone are you? Rigid foam insulation of that thickness will cause condensation problems anywhere north of, say, Atlanta. Bad idea.

Do you have a source for that?  I've got 1" unfaced xps under siding in the midwest with no issues thus far.

If I recall, building science was ok with with the concept when we did it.  I do recall unfaced was necessary to allow the wall some ability to dry out.

MW
« Last Edit: December 17, 2015, 01:35:29 PM by Midwest »

Fishindude

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Re: Insulating my home
« Reply #7 on: December 17, 2015, 01:43:05 PM »
Sounds like you did a good job with attic.

Windows are probably fine.

I would remove and dispose of the old asbestos siding.   And don't let someone give you "the big asbestos scare" regarding that stuff.  You don't need the guys in the white suits to remove it and it shouldn't be too expensive.  that type of asbestos isn't "friable" so it isn't hazardous.  You can simply remove it with normal pry bars and flat bars.  It just has to be packaged separately in plastic bags and the landfill charges a bit more to test and accept it.   

After siding removal, I'd cut or drill some inspection holes in sub-siding to see if there is any insulation in the stud cavities.  If not, I'd blow them full of cellulose.   Not much you will be able to do in areas covered by brick, unless you want to blow in insulation from inside which requires drilling and patching lots of holes in walls, repaint, etc.

Whether stud cavities are insulated or not, I'd then cover the sub-siding with some rigid board insulation and house wrap prior to new siding installation.

Beyond that, make sure all of your door weather seals are good and that you have efficient HVAC equipment and you probably can't do much else.


bacchi

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Re: Insulating my home
« Reply #8 on: December 17, 2015, 02:04:23 PM »

3) Do you have a moisture barrier in the walls? What climate zone are you? Rigid foam insulation of that thickness will cause condensation problems anywhere north of, say, Atlanta. Bad idea.

Do you have a source for that?  I've got 1" unfaced xps under siding in the midwest with no issues thus far.

If I recall, building science was ok with with the concept when we did it.  I do recall unfaced was necessary to allow the wall some ability to dry out.

MW

http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing
http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/can-exterior-foam-insulation-cause-mold-and-moisture-problems

It's also in the IRC, which the first article above references. Rigid foam of 1/4" is ~R-1.5, which is useless everywhere except in the south.

(Yes, the "Atlanta" bit was a wag of where the zones are. Atlanta is further south than I thought and is in 3.)

bacchi

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Re: Insulating my home
« Reply #9 on: December 17, 2015, 02:05:26 PM »
Personally, if I knew there was a vapour barrier on the interior, I would remove the existing siding to free up more thickness and utilize the Roxul Comfortboard product.

Sadly, this doesn't look like it's available in the states.

Midwest

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Re: Insulating my home
« Reply #10 on: December 17, 2015, 03:01:42 PM »

3) Do you have a moisture barrier in the walls? What climate zone are you? Rigid foam insulation of that thickness will cause condensation problems anywhere north of, say, Atlanta. Bad idea.

Do you have a source for that?  I've got 1" unfaced xps under siding in the midwest with no issues thus far.

If I recall, building science was ok with with the concept when we did it.  I do recall unfaced was necessary to allow the wall some ability to dry out.

MW

http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing
http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/can-exterior-foam-insulation-cause-mold-and-moisture-problems

It's also in the IRC, which the first article above references. Rigid foam of 1/4" is ~R-1.5, which is useless everywhere except in the south.

(Yes, the "Atlanta" bit was a wag of where the zones are. Atlanta is further south than I thought and is in 3.)

Thanks.  Rereading your post and the links clarified things.  I believe that's why we went with 1" for our climate zone.