Hi All, I live in Princeton, NJ in a 50 yea old split level home with attached two car garage. Well, the garage (slab on grade, poor glassfiber batts in wall, none in the exposed ceiling) is my woodworking (hobby) workshop. I would like to keep it above freezing year round and be able to use it occasionally for woodworking (50F+). I am looking for help for green methods to insulate and heat. I realize insulating the ceiling (suppose 6" fiberglass batts - or spray foam?) and maybe adding to the walls (currently covered with drywall) - s adding studs and insulation on top? and garage doors would be good. But what to I do to the floor? I still want a future owner to be able to park a car there so insulation and flooring would have to be crush-proof :o) 2x4 sleepers 12" on center and plywood? I'd like to add hardwood flooring to at least parts of the garage for a pleasant environment. Can I use soil heat and quartz electric heaters? There seem to be so many options that I am not sure where to start. Thanks a lot for pointing me in the right direction Patrick

It may be possible to blow celluose into the wall cavities without first removing the (probably R8- R11) batts, but that would be HUGE in terms of lowering the air infiltration rate.

Low density R19 batts lose R big-time when it's colder above than below. If you MUST use batts, go with a high-density R21 "cathedral ceiling" type, if you want it to actually perform. If the ceiling joists are bigger than 2x6 or the spans are short enough you can heap 6-10" of low density cellulose up there, and it'll perform to spec over a much wider temperature range (and would be inherently gap-free.)

If the garage doors aren't insulated types, with good weatherstripping, swap 'em out for some that are. (R10 garage doors aren't too hard to find.)

Digging down and insulating the slab edges at the exterior walls with at least 2" of rigid EPS or XPS on the exterior all the way to the frost line would be in order.

Rather than putting hardwood on a subfloor resting on sleepers, skip the sleepers and float the sub-floor on 3/4"-1" XPS rigid foam (sold as insulating sheathing under siding), for R3.5-R5, and through-screw the subfloor into the slab to anchor it with masonry screws. (Use a roto-hammer/hammerdrill, to make the holes in the slab.)

While the floor loading of 3/4" ply on XPS would be quite good, there could still be some permanent deformation of the foam when parking cars on it. In order to have a fully driveable/parkable crush-proof insulated slab you'd have to pour a fully structural 3" slab atop rigid foam. If you're jackhammering out the original slab first, to with 2-3" of EPS (bead-board) for R8-12 performance at for about what you'd pay for R5 in XPS.

Any windows? Are they double-paned? If not, do the have exterior storm windows?

What sort of heating system does the house have? It may be possible to extend it. Resistance heating is usually on the least-green end of it but cheapest to implement. If the only practical solution is resistance heaters, radiant cove heating (eg: http://www.globalindustrial.com/g/hvac/heaters/cove/radiant-cove-heaters) is more comfortable at lower air temps than other electric heaters (lower air temp=lower heat loss out of the garage= lower power used), and doesn't carry as high a fire-risk as other types of electric heaters.

If the garage has a good southern exposure it may be possible to build-in or add a solar thermal air panel, which would be the greenest way to keep it heated. Even in the dead of winter you can get quite a bit out of them on on a sunny day.

Thank you Dana - that's a lot of information! All of the measures you mention make so much sense, but I won;t be able to do all of them unfortunately - I'll have to prioritize.

Ceiling joists are 2x6 16" on centers so I'll look for the cathedral style batts. And I'll also get quotes for spray foam - I suppose closed cell? Ceiling is approx 500-600 sq ft. A DIY spray foam kit is $600 for what would be about 1 inch thickness = R7, ouch, and I'd probably want R30+ per code?

Windows - there are 3 double hung double pane all of them quite new. One exterior door needs to be replaced with an insulated steel door.

Garage doors - I'll see what I can find - any recommendations?

For the walls, I wonder if I leave the old crap alone and just add to it.

For the floor I wasn't planning on removing the old slab - might make it too big a project! I might as well build a whole new garage and do it right :o) So it's ply over XPS then. I think I'll also cover the 1" high "knee-wall" or whatever is called with foam and add T111 style wainscoting.

For the digging arond the garage, I'd have to remove part of the driveway - arrrgh. And the wife's plants. Not so sure if I want to do that ... (I did dig out and add 2" XPS for an addition that's raised slab on grade two years ago, with somewhat decent results)

Heating - the house has natural gas forced air. Maybe I can extend a duct (doable) ... hmmm :o) just need to cut a hole through the concrete knee-wall (easy).

I currently have one el-cheapo radiant electric heater in there but it's not nearly enough, given the lack of insulation. I'll need to get a subpanel and upgraded wiring in there for the larger 240V tools anyway.

The main thing is that I am spending a few hours a week in there but these few hours are very dear to me - but I don't need to heat it year-round.


How would you prioritize the various parts? From my understanding, it's this order:

1) Ceiling. Heat rises. Cath style bats or spray foam. Open or closed cell?
2) Garage doors, and the exterior door
3) Walls - I am not sure how to best attack it given the old crap batts int he wall. Add additional
4) Decent radiant electric heater
5) Floor- major work if I want to park on it. Doable wit XPS, ply and wood flooring otherwise.

Again, thank's so much for all your help.

BTW wold it make sense to buy one of these infrared thermometers and look at the relative surface temperatures?

Cheers,

Patrick

1) Heat doesn't rise, but hot AIR is lighter than cool air, and will convect to the top. Attic spaces are usually easiest/cheapest to treat though, so it's pretty cost-effective compared to say, slab insulation.) Both open cell or closed cell foam are going to break the bank at R30 fuggedaboudit. High density batts are ~%30 lighter than cellulose at equivalent-R, but more expensive. If the joists can stand a dead loading of 1.2lbs per square foot go with cellulose It's not rocket science to do a decent open-blow with a box-store rental blower. Rental is typically free with $100 worth of material. A settled-depth of 9" would deliver a true R30+ and would run ~1.25lbs per square foot. Blow it to 10-10.5" initial depth to get a settled depth of 9". That would put 4-5" of cellulose as thermal break over the tops of the joists, offering a significant performance boost. A pro might be able to do it for less money than a DIY in some cases. A 25lb bag costs $11 and would give about 20square feet at R30 with an amateur using a beater of a blower. That's ~55 cents per square foot. Open cell foam would run you over 3 bucks a square foot @ R30 (installed), closed cell something like a five-spot.

2& 3) Air leakage is the main thing, and may be half of that would be at the doors & windows, but if history is any guide, 1950s batt-insulated walls are real sieves, and that could dominate. Blowing cellulose in the cavities even at low density would reduce that factor by 90% and bring the steady state R-value up to ~ R12-R13. A pro should probably be able to tell you how easy/hard/possible that is. Some installers are pretty good at figuring out how to yank them out without ripping the whole wall apart, but it's usually possible to squirt something in there even if they can't be pulled.

4) Yes, ceiling-mounted radiant coves are best for your application. They come in 120V versions too, but if you're wiring in 240 that's great! But we don't know just how many watts it's going to take- concentrate on insulation & air sealing first. That and some oil-filled radiator type plug in space heaters will probably give you a rough idea how much radiant cove to buy. The fact that it heats the chairs/benches/ people before it heats the air makes it much more comfortable even at low temp, but avoids the fire hazard of the glowing red spot-heaters, or the annoying fan buzz & wind chill of fan-coil space heaters.

5)Yes, major work. But even if you skip the floor, DO dig down at least a couple of feet below grade on the accessible portions and install some slab-edge insulation all the way up to the foundation sill/stud-plate for the studwall. Install some Z-flashing between the silll out & over the top of the rigid insulation to seal off termite & ant tunneling possiblities, and use EIFS or fibercement with parge to protect the above-grade foam from the elements. The above-grade concrete 5" thick has an R value of less than R0.5, and will DOMINATE the heat loss once the air infiltration is better controlled if you don't insulate it.

The pistol-grip type infra-red thermometers are a good tool to have for anybody doing insulation & air sealing upgrades to a place. They can be had for under $100 these days.

Blue & orange oox-stores often carry R10 insulated garage doors, and have a installation contractors to tap. It's better to get recommendations from locals and deal with the contractors directly though, otherwise it turns into a 3-way argument should anything go awry.

1) Sounds like the spray foam is a no-go. I'll start by looking for a decent insulation contractor

Pity I don't have a picture - the garage has a open cathedral ceiling, about 4/12 slope (not sure, could be 6/12), and 2x6 ceiling joists going the length of the garage every 4 feet. I could install 2x4 across these joists every 16" and hang drywall it, which would create kind of a a dropped ceiling at about 8' 6" or 9' so. That's also less volume to heat and easier to light the space. Then blown-in cellulose would be a no-brainer (we also had some added to the attic after we moved in - big difference!).

The only downside is that I have a 8'x16' platform above the garage doors for extra storage and the dropped ceiling would limit the height for this platform to <2'. Hmmm difficult decision.

2), 3) A pro will have a good idea ...

4) Then that's settled.

5) Sounds like a nice summer project to me. I did almost the same thing - cementboard over the 2" XPS, used a thickened epoxy coat over the seams, painted, and sloped copper flashing under the siding and over the cementboard for drainage

Again, thanks a lot for all the time you took to answer these questions!

Patrick

With a 4/12 roof with one gable attached to the house (conditioned space==no heat loss out that gable) the additional roof + gable area compared to a dropped ceiling area is not huge. Since you're using the loft for storage, insulating the exterior gable and the underside of the roof deck is a viable option. (I'm assuming the rafters are either 2x4 or 2x6?)

On the gable end, fatten it up to 6" with lateral 2x3s set 24" o.c. and use wet-spray cellulose "blown in bag", where they staple a mesh to the framing, and insert a hose behind the mesh through slits. That'll give you ~ R21-R23.

On the roof deck, first spray 1" of closed cell foam ( a bit over a buck a square foot), then fatten the rafter depth up with lateral 2x3s (if the rafters are 2x6) or 2x4s (if the rafters are 2x4) to a total of 7-8". Then use wet-spray cellulose blown-in-bag to fill it out. That will deliver R27-R29 if the total depth is 7" (2x4 rafters) or R31-R34 if the total depth is 8" (2x6 rafters). Either is acceptable from a code point of view as a "cathedralized ceiling.) Since this is a garage, not a constantly conditioned space, you can probably get away without the closed cell foam, but should it ever be converted into 24/7 type living space there would be some risk of creating roof deck rot conditions without it. It's your call. (The inspectors might have issues with unvented roof deck & cellulose-only.) See:

http://www.buildingscience.com/documents/reports/rr-1001-moisture-safe-unvented-wood-roof-systems

Wet-sprayed cellulose (but not dry blown) qualifies as an ignition barrier for the closed-cell foam, so you wouldn't HAVE to put in half-inch gypsum or OSB on the interior, but putting something up (even cheap 3/8" OSB) would better protect and support the roof deck insulation. If you went with a 7/16" OSB interior and skipped the foam you could also go with dry-blown "dense-packed" cellulose, which takes ~1.5x the material, but would give you a similar R to the foam + wet spray solution, and reasonable rot-protection from moisture migration from the interior in your climate zone. (Dense pack cellulose without foam is done all the time in cathedral ceilings over fully-conditioned space in southern New England, which would be even more susceptible than southern NJ due to cooler winter climate conditions.)

I'm not sure how much funding is left, but in NJ there USED to be pretty good subsidies for insulation upgrades. I'm sure the local installers are completely up to date on what's out there, since it's their life-blood in these days of minimal new-construction.

Structurally, roof decks & rafters are better equipped to handle the loading than truss chords or attic joists. I'm thinking an insulated roof deck is the right solution here for more than one reason. If you need/want to go higher-R at a later date, an inch or 3 of rigid foam OVER the roof deck (and under new roofing) can be a good solution that further reduces risk of moisture problems at the roof deck. (My 1920s antique in central MA has 6" rafters. I have less than a decade left on the shingles, and will be adding 3-4" of rigid polyisocyanurate pre-laminated to nail-base decking when it's time to re-roof for an additional ~ R20+.)