Insulating unattached garage from the inside

[dimwittedmoose51]

Hi All: This will be a long post that I've edited down about as far as I can, so bear with me.

I've been reading through many of the insulation/vapor barrier threads and learned a lot from them, but I still have some questions that here to fore, haven't dealt with my specific situation.. I live in NE Iowa sort of on the south end of climate zone 6. The shop is roughly 24x24, 8' walls, "conditioned attic", ridge vent, (but plug it up in the winter), R-11 faced in the 2x6" roof joists (previous owner)) and it's exposed as is the gable insulation on the south side over the garage door. Pretty much nothing in the walls, steel siding on the exterior, insulated double garage door, wood entrance door (will be replaced with a foam core metal fire door next spring), was built in 1969, so likely has no Tyvek between the siding and the OSB board, and the interior walls are 99% painted pegboard.

The goal is to insulate the structure with an eye on cost/benefit and whether the investment in the improvements will decrease the anticipated electric bill and increase the value of the property should we decide or need to sell. I had a 32" wide Defiance steel plate wood stove in the shop for years and the 8" flue went straight up for excellent air draw. I removed it two years ago because I'm getting old enough now that scrounging for free hardwood and splitting it is more work than I want to put in to the comfort of the shop. Considered a propane tank, but city regulations would only allow a 250 gallon tank and in addition to that, I don't like Propane's efficiency when it gets below 20 F and getting the tank refilled was going to be an issue. Thought abut natural gas, but the cost of burying a line from our meter to my shop seems cost prohibitive (since no one would give me an estimate), so that leaves electricity. Extra insulation for expensive electric heat is a given and I have a small 5kw Dayton 220VAC heater from the 70s i used until the temps got below 20F and then I would switch to the wood stove. Last winter when it got cold the Dayton couldn't keep up especially when the wind was blowing. With it pretty much running 24/7, we could expect another $90/mo. added the the utility bill. The building walls and top plates seem to be the primary source of the air infiltration and since there's no sign of the air channel pieces under the R-11 in the rafters, I'm going to assume that sealing the top plates and the stud to OSB board with the Great stuff gun and the sealant that bonds down to 14F. I have purchased a 7500 watt King Electric heater with built in thermostat and two stage operation. I still have the Dayton hooked up, but running both simultaneously would be taxing the capacity of the 6 gauge wire from the house breaker panel to the shop's 60 amp service. Getting rid of the 5 hp 220 volt air compressor or I'd really be in a pinch.

Now comes the part where I have to make some serious decisions.

1. I have a 150' roll of 9' Tyvek and if I sealed all the air leaks I could reasonably access with the foam and then add the R-15 faced batts in the walls, will the Tyvek be a benefit to the insulation project? The steel siding would be a PITA to remove and mark each piece as to it's placing on the 3 walls in order to get the Tyvek wrapped around the building, so would there be any reason I couldn't install the Tyvek up against the interior sides of the 2x4" studs and get the same benefit? IF the Tyvek does allow vapor to pass through it and the kraft paper on the insulaton is facing the warm area of the building there shouldn't be a mold issue or would there be one?

2. Obviously I'll have to replace the pegboard with some sort of sheeting as the foam contractor I talked to said if they came out and drilled the holes and shot foam into the 2x4" cavities, the foam would expand and ooze out the pegboard holes and make a big mess. My shop is loaded with tools and other stuff that I would be lucky just to do one wall at a time and move all the stuff stored by or on the wall I was working on away from the that wall. The contractor would want to do all the walls in one day and he wanted $2500 to do just the walls, so that's not really an option either.

3. Next comes the decision on whether to rip out the R-11 from the rafters and replace it with the R-19 and then fasten the 1/8" paneling/ sheathing to the 2x6's. There's no way I'm going to sheetrock the shop, so thin walled sheathing will have to do. Maybe repurpose the pegboard for the rafter sheeting and save some money, assuming it doesn't crumble......lol

I appreciate in advance any help the garage gurus can provide. I'd like to do this project once and never have to mess with it again. Dismantling even one of the three walls is gonna be a major task.

DM&FS

 

[Kaizen]

Usual certified mess.
First get a mini split that can heat well. Probably a tenth of the cost to run.
Air sealing is your main issue. I’d get some quotes to have an inch of spray foam done as an air seal then use the biggest and best batts you can afford. I used rockwool and although more expensive you can quickly see if we’ll it seals compared to fiberglass.
The attic should have baffles all the way up to the ridge. Can you seal off that space or does it need to be heated? You can also use 4x8 sheets of 2” foam over the whole ceiling in attic. Not cheap


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[dimwittedmoose51]

I can investigate the mini splits, but I have NO use for air conditioning in the shop whatsoever. The rafters will be left open due to the space being used for storage. I get the fact that the heat is rising up there and have thought about rigging a small ceiling fan up there to move the hot air down to ground level, but not sure how cost effective that would be. I may just jump in with both feet on the air seal mission for now. There's no question that's my biggest hurdle. Thanks.

 

[klassenl]

If I understand correctly.....

The only way to insulate properly is to open the walls as far as you can.

Further...doing anything else is of minimal value until you insulate properly.

 

[slowtwitch73]

Don't sacrifice the good for the perfect.. its an older structure. Good thing is you have nowhere but 'up' to go.

Get rid of the attic insulation. That's way too low an R value. 2" rigid foam is also low R Value.

R30 in attic, and just bite the bullet and do one wall at a time yourself. Tear down the peg, insulate, sheet rock.

 

[Kaizen]

I can investigate the mini splits, but I have NO use for air conditioning in the shop whatsoever. The rafters will be left open due to the space being used for storage. I get the fact that the heat is rising up there and have thought about rigging a small ceiling fan up there to move the hot air down to ground level, but not sure how cost effective that would be. I may just jump in with both feet on the air seal mission for now. There's no question that's my biggest hurdle. Thanks.

Can’t make a pull down stair or access door for storage? If you can stop at the ceiling it saves a lot of issues.
Mini splits are also awesome at removing moisture. I don’t mid heat but humid *****. Good luck.


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[i4ni]

Don't sacrifice the good for the perfect.. its an older structure. Good thing is you have nowhere but 'up' to go.

Get rid of the attic insulation. That's way too low an R value. 2" rigid foam is also low R Value.

R30 in attic, and just bite the bullet and do one wall at a time yourself. Tear down the peg, insulate, sheet rock.

I Built a 26x40 dog kennel that consists of a 13x40 enclosed and heated area and a 13x40 under roof but open kennel run area. This thing is easily heated using only a small portable 120 v infrared heater. I'm really amazed how little heat it requires and how cool it stays in the summer with no A/C. I'm not going to give you any advice but I'll describe what I did and you can go from there.

It is a stick frame structure built slab on grade with thickened edges with 2x6 8ft walls setting on sill seal with open face insulation covered with a tight plastic vapor barrier then sheet rock. The ceilinig is vapor barrier with sheet rock The exterior walls are 1/2 osb with Tyvek and fiber cement siding. I caulked every stud space top, bottom and sides. The attic insulation is loose fill fiberglass 12" deep I believe and I used vent chutes with vented soffits and ridge vent plus functional gable end vents . It has a 4/12 shingled roof with 2 foot overhangs and barged gable overhangs. It has 3 36x40 IG casement vent windows(Pella) a 7x9 insulated garage door and a 36" walk in door and 8 medium sized spring loaded dog doors. The dog house/beds are framed over closed cell foam and extend out 3' from one wall and run 36' long. This building is much warmer than my house which is 2x4 famed walls with closed cell foam walls and ceilings. If i ever build another home I will replicate the walls in my kennel caulking and all and add vapor barrier to the ceilings. I don't know what else to contribute the energy efficiency to but it flat works with absolutely ZERO moisture issues. P.S
Located in south central Iowa

 

[bdbecker]

Hello neighbor! I grew up near Parkersburg, now live in Des Moines.

For maximum cost/benefit, start with the ceiling. I know you want to use the rafters for storage, but you'd be better off installing a ladder/hatch to access that area and sheeting the bottom of the rafters/trusses. Use something halfway substantial like sheet rock or OSB - 1/8" paneling is not going to hold up over time. I would keep the R11 in place and sheet over it. Blow in additional insulation to achieve something close to R40, with R50-R60 being better (not much cost benefit going much higher than that). Also, don't forget to install vent baffles.

For the walls, I'd go with kraft faced R13. I've read enough about plastic vapor barriers to be skeptical of them, at least in the midwest where we see huge temp swings. If you were dead set on having it, use unfaced R13 batts in the walls and install plastic sheeting on the inside face of the wall.

Here is some additional info on vapor barriers - sounds like for us, a semi-permeable barrier (like kraft paper) installed to the inside is probably the best bet:
https://www.certainteed.com/insulation/resources/do-i-need-vapor-barrier

Don't waste any time on installing the Tyvek - it is not a vapor barrier. House wrap is more like a breathable rain jacket - it stops liquid water from soaking your your sheeting in case of a siding failure, but is breathable to prevent moisture buildup and mold. The way in which you describe using it will not offer much benefit.

 

[Toyomech]

Its gonna be hard to come up with a solution thats easy, permanent, but also cheap. Be aware that the metal siding is a vapor barrier. I wouldn't use plastic inside mixed with batts. Also, air sealing the soffits with permeable insulation against the roof and no vents, then adding propane in particular, especially in a cold climate zone, is a case study on moisture problems.

I get why the contractor wants to do it all in one shot. It wouldn't be profitable for them to come out 4 separate times for this without increasing the price by a lot.

I think adding a ceiling is your best bet but even that is gonna require moving your stuff in order to roll scaffolding or use ladders safely etc. I think the saying buy once, cry once applies here. Spending money on bigger heaters, paying more on energy monthly, putting hours of personal effort and then not getting the desired outcome or having mold issues that would require major work in the end isn't worth the potential savings. Hope I didn't offend you in any way just don't want to see you wanting to save a few bucks and then needing to spend a ton of money in the end because the roof rotted out or worse.

 

[CraigStu]

I would seal up that attic first thing. You are losing some huge % of your heat heating a space you are not in. Drywall on the ceiling will work fine. If the ceiling joists are 24 OC pick a spot close to the roof peak to put your access panel. A 2x4'x1/2" plywood will be fine. If the joists are16 OC, you need to cut out a 4 ft piece of one of them and box in your opening. If you don't already have one, buy a good quality 8ft step ladder. Set it up w/ a piece of rope through the top of the inverted V tied to an eyebolt on one side and use a dog leash type connector on the other. Run a rope from the base of the ladder to a pulley in the ceiling, through a pulley at the wall and down to a cleat at chest height. Store the ladder against the ceiling. Let it down for attic access. If you need it somewhere else undo the dog leach rope connection and take it away.

 

[aussieblake]

Personally I don't see the advantage of using the house wrap material in your situation. If it were me, I would expose the walls and seal where the walls bottom and top plates meet the sheathing (assuming there is sheathing exterior sheathing besides the metal exterior), use a product that fits the application, could be caulking sealant or expanding foam. Once the walls are open, after you remove the peg board, on a sunny day shut the doors and turn off the lights, look for light infiltration, where there is light there is most likely air infiltration. Once sealed install your insulation of choice, this is limited only by your budget and the walls physical limitations. Honestly I am not sure a mini split would be a application as the ones I have dealt with are basically a heat pump and in the lower temps your structure would see they are not very efficient. Electric heat is convenient, just depends on your overall cost per KWH. Have you considered lining the walls of the structure with Plywood (1/2"-3/4") or even OSB? It makes hanging tools or other items easier than peg board, at least for me. Just a thought, I did it in my shop. For the ceiling, you should allow a way for air to travel along the underside of the roof deck, baffles or whatever you can afford or come up with. I would then insulate with batts and then cover the batts with some type of sheathing, as mentioned (in a previous reply above) OSB would be a good option but also consider corrugated metal. Sounds like your budget is your limiting factor, there are lots of ways to tackle your project, you just have to decide which one meets you needs as far as budget and the ability for you to install. I do like spray foam, but it costs more and sounds like it is not a solution you are willing to utilize. Good luck with your project!