Winter Is Coming - DIYer Insulation

My built in 1998 house is COLD. It's got in-floor radiant heat that can make the floor really cozey, but the house's high ceilings and "around the outside" layout mean that the places where we spend the least amount of time are the warmer, and the master bathroom, bedroom, etc are all cold. 

The first improvement I hope to make is insulating the external foundation at the stem wall the whole way around the house. That area bleeds a lot of heat from the slab. Big thanks from the folks who assisted with that on here. 

I also hope to reinsulate and seal our master bathroom, easily the coldest room in the house. 

Currently, I'm torn between XPS Foam board sheets cut, stuffed tightly, and sealed with expanding foam in the exterior bathroom walls, or if I should do a DIYer spray foam. 

Any suggestions?

No help with the insulation recommendations, but I'll throw out my ideas anyway. This may not be all that helpful, but heat rises. Most (definitely not all) heat escapes through the roof. You generally (not always) get better returns by adding more insulation to the attic. 

Also, if you have ceiling fans, run them in reverse. 

Bought a converted camp-renovated-into-a-year-round home this past summer.  I am also cold, and very much following along for info...

Assuming you're pulling all the drywall off in the bathroom, I suggest spray foam unless it is fantastically more expensive.  It skins over to form a continuous vapor barrier on the inside.  The XPS will do the same in conjunction with a filler, but you'll need to be more careful about the fit and sealing.

I also suggest more attic insulation if you have access.  Recommended value for roofs / attics used to be something like R-19.  Nowadays it's anywhere from R-30 to R-42.

We're having our flat roof dormers redone (over 2 of 3 bedrooms and a bathroom).  I'm adding R-15 unfaced rock wool over whatever is up there from 1967 while the sheathing is off, and then 1-1/2" polyisocyanurate over the sheathing under the new membrane.

I've got loads of access to the roof, but my budget right now is focused on updating the house in a market that is soon to be saturated with newer homes that are not only designed better, have nicer finishes, but are also more efficient. The only thing my house has got going for it is lot size and single story (many of the newer homes in town are tiny lots and multi-story). 

So, with that in mind, I'm interested in ideas to make the coldest rooms more comfortable without spending $10,000+ on re-insulating the entire house.

I agree with other people. Do the ceiling first. It shouldn't cost $10k to add more insulation to the attic. I think it cost me $2.5k for someone else to my split level (so two attics) 1950s 2200 sq foot house. If you do it yourself it should be a lot cheaper.

Also check the windows those can leak a lot. I recently redid an 8x10 bonus room that we converted from a side porch by a previous owner. The walls and ceiling had installation but it was freezing cold in winter and burning up in the summer. I took the trim of the windows and there was not insulation directly around that so I filled that area with Great Stuff and put weatherstripping under the opening part of the window. The difference in the room is amazing.

Roof isn't an option. Wife wants a more modern house. If I spend too much time and money insulating the roof, I don't end up with a more modern house, just a warmer one. 8 months out of the year our house is completely comfortable without any air conditioning or heat. I don't want to blow my entire budget on one aspect of the home that might not be a forever house.

Lets focus on a room by room approach. The bathroom is being remodelled. None of the other rooms are being touched. Therefore, I want to focus on the bathroom. 

I should note that I've got single story, 1650sqft home with approximately 2200sqft of roof space. While yes, better insulating the roof would make massive improvements in efficiency, it's also a huge job. 

In reply to pheller :

Are there windows in the bathroom? I'd start by looking at those as a place to make a large improvement.

From what I have seen I'd try to go the spray foam route over the board sheets but I am no expert to be honest.

Spray foam can be difficult to get right. Common complaints are off gassing, shrinkage in the cavity, etc.

I'd think a DIY'er could have better, more consistent results with foam board and sealing the edges vs full spray foam DIY.

The bathroom window isn't actually that terrible. I've got a Seek Thermal Compact camera for the iPhone and I was surprised to see my windows are generally pretty good. Some thermal bridging happening around the window frame, but no significant air gaps. 

Again, because of the remodel, that window is being completely redone, moved, widened, etc. 

The bathroom has two "cold walls", 1 is the outside 6", one the garage also 6" thick. Both were originally fitted with fiberglass batts. I suspect the area behind the shower either wasn't insulated, or the insulation has detached and slumped. The area is bright red when I do exterior thermal camera imagery during the winter. 

STM317 said:

Spray foam can be difficult to get right. Common complaints are off gassing, shrinkage in the cavity, etc.

I'd think a DIY'er could have better, more consistent results with foam board and sealing the edges vs full spray foam DIY.

I tried some diy spray foam: the learning curve is steep and it is an expensive setup. If you are thinking spray foam hire an insured professional. You will likely notice your chemical costs alone are not much lower than what pro's with experience can do.

Foam board and spray foam edge sealing (buy a refillable gun) is easy diy and great for air sealing.

If you don't need to air seal fiberglass/cellulose/rockwool will get you more R value for your $.

If bathroom is the coldest room, what about adding attic insulation just over the bathroom? Wouldn't even need to blow it in, could just get a couple batts/rolls of unfaced to do just the bathroom ceiling area. Also, cold air may be drafting in through the vent fan shaft or insulation may be thinner around that area in the attic.

I just checked:

I've got R-38 Fiberglass batting across the entire attic space. Including over the bathroom. 

I've got nothing under the roof. 

STM317 said:

Spray foam can be difficult to get right. Common complaints are off gassing, shrinkage in the cavity, etc.

I'd think a DIY'er could have better, more consistent results with foam board and sealing the edges vs full spray foam DIY.

Lot of work compared to spray foam.  Only a 30'x30' area of my attic is joists. But since I have so much left over 2" foam I did it and then will have it sprayed to 1/2 fill the  the bays with foam.  The rest I'll fill with Fiberglass.  (8" beams ) 

In reply to pheller :

Heat rises. Nothing in the attic means you'll pump a lot of heat in the room and it won't stay around very long.  
I have 12 inches of foam  over my 28 foot ceiling. Because foam does such a wonderful job of keeping heat in. If you check the temperature  it's exactly the same from the floor to the ceiling. 

Let me clarify:

I've got 6" R-38 battling between ceiling joist/rafter bays. 

I've got nothing hung between the roof trusses against the roof sheething. 

My attic is unfinished, unconditioned space with gable vents. 

Really, my post was designed to focus on the bathroom's exterior wall - a place where I currently have issues with insulation slumping in the stud bays, and is also the coldest room in the house. It's an 8' section of wall. I don't need to reinsulate the entire house. I just need a strategy for a moisture containing section exterior wall. 

Not supposed to have anything against the underside of the roof sheathing. Only on the attic side of the ceiling, like you have. 

Do close up the attic vents during extreme cold, but don’t forget to open them back up. 

It might help to add some additional un faced insulation over the ceiling joists, only over the “cold” rooms. 

03Panther said:

Not supposed to have anything against the underside of the roof sheathing. Only on the attic side of the ceiling, like you have. 

Do close up the attic vents during extreme cold, but don’t forget to open them back up. 

 

The exception is if you use those plastic vapor paths to allow the  roof to cold vent. Then you can foam away. 

In reply to frenchyd :

I’ve seen what I think those are, but never owned property far enough in the “great white north” to need em!

pheller said:

Let me clarify:

 

I've got 6" R-38 battling between ceiling joist/rafter bays.

Wait a minute, is there a mix up here?

6" thick fiberglass is R19 (actually 5.5 inches)

R38 is almost 12" thick

I know you're really just wanting to do the walls while you renovate that bathroom anyway. That makes sense, especially if the insulation there is failing (again, I'd do foam panels and seal the edges). But if all you have in the attic is 6" thick R19, that's way low for anywhere in the US and adding some there would really help your comfort level. It might even make your wife happier and less likely to want to move every 3 years.

Recommended attic R values by region:

What surprises me is that the one bathroom wall shows up bright red on FLIR.  Something is going on there.

Triple check window gaps.  They are notorious.  I solved 80% of my cold air issues in my 1900s house that way.  The windows had been replaced with very nice vinyl  2-pane upgrades in 2012, but installed so poorly.  The walls and sills weren't straight, so they just shoved them in and screwed them leaving significant gaps.  I pulled the casing trim off.  Some areas were pretty tight so I just caulked those.  Some areas had 1/4-1/2" and I sprayed those gaps with expanding foam.  Others were huge 2" gaps (not likely in your house) where I stuffed fiberglass.  Then I put a bead of caulk around where the windown frame meets the sill and sides.  Huge help.

Interested to see what's behind that red wall.

Have you considered insulating the ceiling/attic? Kidding. 

Good info here that is relevant to my interests. 

Thanks Curtis. 

I might have 12" R-38 up in the ceiling (it's labeled R-38) but it's not 12" tall anymore. Maybe 10"? It's just lost some of it's loft.

The bathroom hot spot I believe is because either A) there is no insulation behind the shower or B) the insulation has "slumped" - falling down to the bottom of the stub bays. 

My plan to rectify and prevent that in the future is going to be 5" "cut and cobble" with rigid foam and spray foam around the edges. It's only a few bays, so the extra labor doesn't bother me. This is my plan unless someone convinces me stuffing cellulose or rockwool bats in those exterior studs bays.

pheller said:

...

My plan to rectify and prevent that in the future is going to be 5" "cut and cobble" with rigid foam and spray foam around the edges. It's only a few bays, so the extra labor doesn't bother me. This is my plan unless someone convinces me stuffing cellulose or rockwool bats in those exterior studs bays.

Foam board is R-10 for 2" thick at best. You can get the board easily in 0.5", 1" and 2" thickness with varying R value based on size and material. 

Rockwool etc will give you R-15 to R-20 to fill a stud bay depending on how deep your stud bays are and what kind you get.

You could stack foam board to fill the stud bay depth and you would have a higher R value, but it will cost much more in materials. It will be really good for air sealing if you foam the gaps. Time, labor and material costs way higher here. 

If you are not worried about air sealing (as you have already addressed it or do not want to) simply putting in new bats between the studs would be quickest and easiest with minimal expense. 

There are only really varying degrees of more or less right answers, million ways to skin a cat. Just slow down the heat transfer.