Some questions for trying to improve the heat loss at my mothers house.   I have an energy audit scheduled for this week.

The house was built in the 80's with double stud construction.  Exterior walls are 10" thick filled with pink fiberglass. with a poly barrier under the sheetrock, exterior sheething is just boards, roofing felt, then board and batten siding, with anderson double pane casement windows.

Even with all that, it is still pretty drafty on windy days. you can feel the air leakage at the outlets/switches, and where the floor meets the wall.


Tearing out all the sheetrock is out of the question. but I have been thinking about taking down the siding to try and seal it up.  (have some rodent issues that need to be sealed too)

The ideas I have:

R&R siding, install some sort of a breathable air proofer..

R&R siding, replace board sheathing with plywood/osb install some sort of a breathable air proofer..

R&R siding, remove board sheathing do a backwards flash and bat by removing all the existing fiberglass and hitting the now exposed poly/studs with a coat of spray foam, replace the fiberglass, and install plywood/osb install some sort of a breathable air proofer..

Would I cause vapor issues sealing with spray foam?  Would cellouse or somthing different than fiberglass be worth the extra $ over just re-using the existing insulation?

Looking for suggestions or comments

have you had an energy audit/ blower door test? that would be the first step. 2: Seal the rim joist/sill area - it's very likely there are major air leaks in that area. 3:You do not need to add insulation, but you do need to address air sealing. Remove siding, go over sheathing with ZIP sheathing, caulking edges with acoustic or urethane caulk and taping all joints. Pay particular attention to bottom of walls if they extend outboard of foundation. Seal attic/roof penetrations. Pretty involved & complicated procedure but these measures can solve the problems.

I think your major issue will be the board sheathing exterior. I ran into that once before and found the exterior boards to be the problem.

will using somthing like zip system cause any issues with moisture because there is already a layer of poly (even though it isn't sealed to the metal electrical boxes?

update:

Energy audit shows 2726 cfm 50 for leakage, with a large amount of that coming up from the un heated basment.

When calculating ach, is the entire volume of the building used, or just the heated volume?

doing the math shows 13.6 ach50 (converting cfm to cfh and dividing by heated volume), or 8.4 ach (converting cfm to cfh and dividing by total building volume)

Have some work to do sealing the basement (sealing 4 leaky windows, a door, and a bypass to the roof along the chimney then CCSF the rim joist) then a retest.

Interesting. Is the fiberglass batts or blow in? I would be very interested to know how they installed the batts in a double studded wall to prevent cavities where air could move around.

You could always get cellulose blown in without removing all of the siding. I looked at getting this done but my house has 1/2inch polyiso on the outside of it instead of plywood so I am afraid it would buldge or break with cellulose blown in. My only option at this point is going to be to take down some drywall and use CCSF. Not a bad option in my opinion since they skimped on the batts because of the polyiso and put in R11 batts. Now the polyiso has holes in it from the old siding and new siding nails. If I ever side again there will be more on the outside. I dont even know if there is even a service where someone shows up, takes your siding off, adds rigid foam, and then puts the same siding back up?

As for the basement, I put CCSF in my crawl and like it. That is really the only good way to get rim joists. I plan to go back in before the winter and add another inch of CCSF and then hit it with a pass of OCSF.

Posted By krom on 18 May 2014 01:25 PM
update:

Energy audit shows 2726 cfm 50 for leakage, with a large amount of that coming up from the un heated basment.

When calculating ach, is the entire volume of the building used, or just the heated volume?

doing the math shows 13.6 ach50 (converting cfm to cfh and dividing by heated volume), or 8.4 ach (converting cfm to cfh and dividing by total building volume)

Have some work to do sealing the basement (sealing 4 leaky windows, a door, and a bypass to the roof along the chimney then CCSF the rim joist) then a retest.

If the cfm50 number included the unheated basement during the test you need to include it in the ach. If the basement isnt part of the homes conditioned air, like a sealed crawlspace, it shouldnt have been a part of the test and the access to that area should have been closed off and not included in ach.

Right, ACH used in heat loss analysis should only include the living space volume and the blower door test should have only been done for this volume too.

To ascertain if your proposed wall assembly will have any moisture issues, one would need to know the temp and relative humidity of the living space and the outdoors along with the details of the wall assembly layers. You can use our building assembly moisture analysis software to investigate this:

http://www.borstengineeringconstruction.com/Building_Assembly_Moisture_Analysis_Calculator.html

Please be sure to read the associated software instructions so as to fully understand/consider the limitations of this ASHRAE Glaser dew point analysis approach.

Its a full basement with a slab floor, and isn't heated on purpose... but the furnace is down there, and the door/stairs to it are so poorly sealed that the blower door test pulled a massive amount of air up the stairs...

It sounds like it should be included as conditioned space even though you aren't heating it and you should treat/airseal foundation walls and floor as part of your thermal boundary.

i would include it because its a full basement that could be heated if you want it to be. The furnace and I'm assuming ductwork are in the space. I think it would be a mistake to airseal the first floor to the basement, treat the holes that connect to the outdoors first.

the basement definitely sounds like the place to start. you cannot tell what you need to do to your house until you repair the air leaks in the basement, and you'll probably be surprised at how much more comfortable the house becomes after that is done. Start with the rim joist/sill area, add an exterior weatherstripped door to the inside of the bulkhead area; those will probably take care of the majority of the problems.

Thanks,

I plan on having the rim joist area done with CCSF, sealing the windows, and building a new door to the bulkhead. FWIW heating is done with a boiler and baseboard.

Posted By Bob I on 25 May 2014 08:52 AM
the basement definitely sounds like the place to start. you cannot tell what you need to do to your house until you repair the air leaks in the basement, and you'll probably be surprised at how much more comfortable the house becomes after that is done. Start with the rim joist/sill area, add an exterior weatherstripped door to the inside of the bulkhead area; those will probably take care of the majority of the problems.

Not all air leakage carries the same energy use consequences- some are much worse than others.  The band joist and foundation sill leakage of most homes (even those built with foamy sill-gaskets) usually exceeds all of the window & door air leakage combined.  Worse still, being near the lowest part of the building that leakage is a major contributor to the 24/365 "stack effect" infiltration, being the entry point at the bottom of the stack. It is as important to seal the bottom as it is to seal the top of the stack (the attic floor/upper floor ceiling).  Take care to seal any electric/plumbing/flue chases that run from basement to attic too.

Air leakage at roughly the mid-elevation of the house has comparatively low energy use consequences.  This is sometimes referred to as the "neutral plane" level, since stack effect or not, it's at about the same  pressure as the great outdoors, and doesn't drive continuous infiltration through those leaks, even if a blower door (or high wind) does.  A square inch of air leakage at the neutral plane tests the same as a square inch of leakage at the attic floor or foundation sill in a blower door test, but from an energy use point of view it's an order of magnitude or more lower in importance.

Any home with the boiler in the basement will benefit from insulating the foundation walls, even if there is insulation between the joists.  With the boiler &  some of the distribution plumbing on the exterior of the thermal boundary the thermal losses from the  boiler & distribution are truly losses when the above grade portion of the foundation is only ~R1 concrete or CMU, but if insulated the those losses accrue to the basement, lowering the net heat load for the house, even if you're not actively conditioning the basement to the same temperature as the rest of the house.