hey there! We own a 1.5 story ranch with two upstairs bedrooms (dormer) in northern NJ. In one upstairs bedroom, we removed the contact papered over wood paneling, thinking there was sheet rock underneath. This turned into a bigger job than expected, because only 1/3rd of the room was sheetrocked. I've already put in place the sheet rock for the entire room (except a piece or two). A guy at work heard what I was doing, and is strongly incouraging me to upgrade the insulation (sad looking R13? between 2x6 roof rafters). So now, I'm trying to figure out if we have the budget to insulate well enough to make a difference. And if my budget allows a "good" setup. And I want to make sure a "cheap" solution won't cause moisture issues. The roof has soffits along the eaves but no vent at the top of the roof. Most of the "attic" is the "insulated" bedrooms which is above the living spaces and about a third is open to the uninsulated attached garage. Looking around, I'm not totally confused. Fiberglass doesn't seem like it will do much and I'll have to take all the sheet rock down. Spray foam seems great, other than the sheet rock needing to come down and it not being fire resisent (we heat with a wood stove whose chimney goes right through this room). I heard of just putting 1" rigid foam up over the existing fiberglass/sheetrock, and then re-sheetrocking over that. Sounds to be a pain considering but an option. The plus is that it is also an air seal. Hoping for some opinions here... Our budget is nil at the moment, the cheaper the better. Another bun in the oven and such.

If your budget is nil, then don't start anything until it can be done right

Posted By cmkavala on 05 Aug 2012 06:30 PM
If your budget is nil, then don't start anything until it can be done right

Too late in some regard. :) There is a budget for a low budget fix (fiberglass or one layer of xps/iso boards) If I can do it in stages, I would pursue it (e.g 1" foam put up now and dense cellouse later).

Posted By nikkihorz on 05 Aug 2012 06:47 PM

Posted By cmkavala on 05 Aug 2012 06:30 PM
If your budget is nil, then don't start anything until it can be done right

Too late in some regard. :) There is a budget for a low budget fix (fiberglass or one layer of xps/iso boards) If I can do it in stages, I would pursue it (e.g 1" foam put up now and dense cellouse later).

If you are already sheetrocking, I would just do the fiberglass.

When it comes time to re-roof, putting up 4-6" of rigid polyiso over the roof deck, held in place with 2x furring through-screwed 24" o.c. to the structural rafters with timber screws, and mounting a 1/2" OSB nailer deck to the furring allows you to vent the nailer deck, and seal up the old soffit venting. Insulating at the roof deck and sealing the attic venting converts any kneewall-spaces on the half-story into conditioned space, and those spaces will track interior temperature & humidity.

For insulating fire-resistant clearances to foam or wood around the flues, use a wrap of unfaced R13-R15 rock wool batting, but be sure to air-seal with sheet metal to keep it from becoming a 24/365 infiltration leak.

If you have sufficient lead time, you can get pretty good reclaimed roofing iso (from commercial demolition & re-roofing) a fraction of the virgin-stock price. In my area I have multiple vendors, but if you can't find a source, insulationdepot.com will ship nationwide if you can take a truckload of the stuff.

Posted By Dana1 on 06 Aug 2012 04:23 PM
When it comes time to re-roof, putting up 4-6" of rigid polyiso over the roof deck, held in place with 2x furring through-screwed 24" o.c. to the structural rafters with timber screws, and mounting a 1/2" OSB nailer deck to the furring allows you to vent the nailer deck, and seal up the old soffit venting. Insulating at the roof deck and sealing the attic venting converts any kneewall-spaces on the half-story into conditioned space, and those spaces will track interior temperature & humidity.

For insulating fire-resistant clearances to foam or wood around the flues, use a wrap of unfaced R13-R15 rock wool batting, but be sure to air-seal with sheet metal to keep it from becoming a 24/365 infiltration leak.

If you have sufficient lead time, you can get pretty good reclaimed roofing iso (from commercial demolition & re-roofing) a fraction of the virgin-stock price. In my area I have multiple vendors, but if you can't find a source, insulationdepot.com will ship nationwide if you can take a truckload of the stuff.

Thanks for the great roofing and chimeny tips. "Unfortunately" the roof is only a few years old and I hope not to be reroofing anytime soon.

In that case, concentrate on air-sealing the place. At just about any R value the whole house air infiltration rate becomes a large fraction of the heating load, and can often be reduced dramatically at relatively low expense. (Air leakage will be a much lower fraction of the cooling load, but that decreased latent-load is still important in hazy-sticky NJ summers.)

In 1.5 story houses with knee-walls that are soffit-vented there are usually huge thermal bypasses from one kneewall-attic to another between the floor-joisting. Under wind-loading air can move fairly freely in one side and out the other. It's a time-consuming PITA, but cutting and stapling cardboard air dams that fit between the joists at the bottom of the kneewalls that get sealed on all edges with 1-part foam helps.

If the kneewalls are batt-insulated with no facer on the attic-space side it will underperform it's R-value by about 30-50% under the temperature extremes. Using a vapor permeable air barrier (housewrap works, but so does sheet-cardboard) stapled to the studs and edge sealed (use can-foam or construction adhesive) to the studs to cover the fiber insulation will bring the batt performance closer to it's ASTM C 518 labeled performance. This also lowers the air-communication between the conditioned space and the outdoors.

If this place has a full basement, sealing and insulating the foundation sill and band joist with 1-2" of closed cell spray polyurethane (or 2-4" of cut'n'cobbled EPS or XPS foam-board sealed at the edges with can-foam) reduces the total "stack effect" infiltration of the house by lowering the cross section of leakage at the bottom of the stack. This is the single-most overlooked air leak in most homes, and usually greater than all of the window & door leakage combined. Insulating the basement with an inch or two of rigid EPS or XPS (seams & edges sealed with can-foam) trapped to the wall with an UNFACED-batt insulated studwall can also cut the total heat load by 15-20% for most 1 or 1.5 story homes. This can be done pretty cheaply using reclaimed roofing-foam that is a fraction of the cost of virgin stock. As with reclaimed roofing iso, check craiglist for local sources or insulationdepot.com. (Fiber-faced roofing iso can also be used for foundation wall apps, but keep the bottom edge above the high-water mark if the basement has a history of flooding. The above-grade portion of the foundation wall is more than 50% of the issue, but insulate as low as you reasonably can.)

The relatively low-R roof is more of a peak-cooling load and comfort issue for the upper floor than anything else. After you've nailed every air leak you think you can find, higher an insulation contractor specializing in air-sealing to blower-door-test & remediate the rest of the low hanging fruit that you missed (some big leaks are harder to find than others.) Don't waste time worrying about making the place "too tight" for indoor air quality, that is VERY difficult to achieve in a retrofit, especially on a 1-1/2 story. (And if you're lucky enough to get it down to under 2 air exchange under 50 pascals pressure in a blower door test, declare victory and start thinking about installing an energy-recovery ventilation system to guarantee proper ventilation to every room.)

Posted By Dana1 on 07 Aug 2012 11:18 AM
In that case, concentrate on air-sealing the place. At just about any R value the whole house air infiltration rate becomes a large fraction of the heating load, and can often be reduced dramatically at relatively low expense. (Air leakage will be a much lower fraction of the cooling load, but that decreased latent-load is still important in hazy-sticky NJ summers.)

In 1.5 story houses with knee-walls that are soffit-vented there are usually huge thermal bypasses from one kneewall-attic to another between the floor-joisting. Under wind-loading air can move fairly freely in one side and out the other. It's a time-consuming PITA, but cutting and stapling cardboard air dams that fit between the joists at the bottom of the kneewalls that get sealed on all edges with 1-part foam helps.

If the kneewalls are batt-insulated with no facer on the attic-space side it will underperform it's R-value by about 30-50% under the temperature extremes. Using a vapor permeable air barrier (housewrap works, but so does sheet-cardboard) stapled to the studs and edge sealed (use can-foam or construction adhesive) to the studs to cover the fiber insulation will bring the batt performance closer to it's ASTM C 518 labeled performance. This also lowers the air-communication between the conditioned space and the outdoors.

If this place has a full basement, sealing and insulating the foundation sill and band joist with 1-2" of closed cell spray polyurethane (or 2-4" of cut'n'cobbled EPS or XPS foam-board sealed at the edges with can-foam) reduces the total "stack effect" infiltration of the house by lowering the cross section of leakage at the bottom of the stack. This is the single-most overlooked air leak in most homes, and usually greater than all of the window & door leakage combined. Insulating the basement with an inch or two of rigid EPS or XPS (seams & edges sealed with can-foam) trapped to the wall with an UNFACED-batt insulated studwall can also cut the total heat load by 15-20% for most 1 or 1.5 story homes. This can be done pretty cheaply using reclaimed roofing-foam that is a fraction of the cost of virgin stock. As with reclaimed roofing iso, check craiglist for local sources or insulationdepot.com. (Fiber-faced roofing iso can also be used for foundation wall apps, but keep the bottom edge above the high-water mark if the basement has a history of flooding. The above-grade portion of the foundation wall is more than 50% of the issue, but insulate as low as you reasonably can.)

The relatively low-R roof is more of a peak-cooling load and comfort issue for the upper floor than anything else. After you've nailed every air leak you think you can find, higher an insulation contractor specializing in air-sealing to blower-door-test & remediate the rest of the low hanging fruit that you missed (some big leaks are harder to find than others.) Don't waste time worrying about making the place "too tight" for indoor air quality, that is VERY difficult to achieve in a retrofit, especially on a 1-1/2 story. (And if you're lucky enough to get it down to under 2 air exchange under 50 pascals pressure in a blower door test, declare victory and start thinking about installing an energy-recovery ventilation system to guarantee proper ventilation to every room.)

You really hit the nail on the head! I was avoiding some of those air infiltration spaces because of the headache and hope it wasn't doing "too much harm". The soffits open right into the floor joists into the other room and even though there is faced fiberglass and a plastic sheet with holes, it just looks cold! And our basement (full and crawl) is rather drafty (bad door). Sealing down there I cringed at, just due to the magnitude of it all. But bit by bit might be the best way to do this all. I'll stock up on some cardboard and look around for foam deals on craigslist! Thank you again for the awesome details and advice!

The plastic sheeting in the kneewall spacing needs to be removed- it's a powerful vapor barrier that will condense on the underside in winter despite having rips or holes. Houswrap makes a pretty good flexible air barrier, and itwon't trap water vapor in the assembly.

If the faced fiberglass (floor or wall) has the facer on the exterior side of the assembly rather than facing the conditioned space side it's potentially a problem, but only a big problem if it's a foil-facer (which is an order of magnitude more vapor-retardent than kraftpaper facers.) If that's the case, investigate- peel back the facer in a few places and see if there is any hint of mold in the outer portion of the insulation. This is more likely to happen in the middle of a bay between the studs than right next to a stud, since the thermal bridging of the stud keeps it somewhat warmer (= more hours at above-condensing temperatures, dryer on average than in the middle of the batt.)

Posted By Dana1 on 08 Aug 2012 03:22 PM
The plastic sheeting in the kneewall spacing needs to be removed- it's a powerful vapor barrier that will condense on the underside in winter despite having rips or holes. Houswrap makes a pretty good flexible air barrier, and itwon't trap water vapor in the assembly.

If the faced fiberglass (floor or wall) has the facer on the exterior side of the assembly rather than facing the conditioned space side it's potentially a problem, but only a big problem if it's a foil-facer (which is an order of magnitude more vapor-retardent than kraftpaper facers.) If that's the case, investigate- peel back the facer in a few places and see if there is any hint of mold in the outer portion of the insulation. This is more likely to happen in the middle of a bay between the studs than right next to a stud, since the thermal bridging of the stud keeps it somewhat warmer (= more hours at above-condensing temperatures, dryer on average than in the middle of the batt.)

LOvely! Thanks for pointing that out. I get confused which way the kraft/foil go depending on the situation. We have both foil and kraft backed batting in that area, bothing facing outward. I can't wait for the weather to cool down so I can investigate a little easier.

Most of northern NJ is on the warm edge of US climate-zone 5, but zip-codes matter- the very NW tip is the cold edge of zone-5. In the somewhat more mixed climate of zone 4 it's generally better to avoid highly vapor retardent materials in the stackup, but keep the lowest-perm layers on the conditioned space side.

In zone 5 it's more critical to allow the wall/ceiling assemblies to dry toward the exterior, and putting even a kraft facer (~0.4 perms) on the exterior side can be a problem for winter moisture accumulation, but a FOIL facer (~0.01 perms) is courting disaster, requiring you to keep the conditioned space uncomfortably dry from December-February to limit moisture accumulation in the batts. Since the moisture accumulation is in the batts, not wood, the risk to the wood is pretty low (the studs will run warmer due to their higher thermal conductivity remember), but it would still incur a (temporary) loss of thermal performance of the insulation and run a risk of mold.

One solution would be to put R5+ of rigid foam on the attic-space side of the 2x4 kneewalls, which would raise the average temp at the facer to above the ~40F dew point of the conditioned space air. But on the attic floor the foam-R would have to go much higher to achieve that- it depends on the actual joist depth & the total fiber insulation thickness. Of course, getting sheets of rigid foam into those spaces can be damned-near impossible too.

Peeling the facers and covering the fiber with housewrap would work, but simply slashing the facers won't- vapor diffusion is a cross-sectional area thing, not an air-tightness thing. A tight array of puncture holes on a 1/4" grid would do it, but replacing the batts with unfaced R15 high density "cathedral ceiling" batts and covering them with housewrap would be less work (and higher performance.)