Heating garage with apartment upstairs

[pcampbell]

I'm thinking about heating our 28x28 garage that is being built up now. We have not done insulation yet. The stairs to apartment are inside of the garage which I was planning to keep just above freezing around 38F. I was planning to heat it with a Rinnai direct vent propane heater which allows you to set it to 38F (I think maybe even 36F). They are not super efficient (81-82% AFUE), but easy to install and relatively cheap, and allow low set points.

My thought was to insulate all 6 sides of the upstairs apartment, then insulate on all 4 walls of the garage (the slab and garage doors are insulated). An exterior door separates the apartment from garage.

Question... If we do closed cell spray foam, do we need to put drywall on the walls of the garage or can we leave it open?

Is drywall generally required between ceiling of garage and apartment?

 

[Bluevista]

All garages have to have fire rated 5/8" drywall between them and any living space around me.

 

[pcampbell]

Further question... If I heat the garage to 38F ... can/should I put an inside tankless hot water heater in the garage rather than the apartment (where there is not much good room to do it...).

 

[Bretny]

Same on the fireproofing here. Heated or not its mandated even if you buy a 1970s house.

 

[pcampbell]

Interesting my contractor left it out of the proposal to finish, which I thought was a little odd. He did put it in there, but left it as optional.

So let's assume we do spray foam on garage ceiling, then 5/8 drywall. What should we do with the walls in the garage?

I am guessing that Roxul and drywall will be around the same price as spray foam and no drywall.

Now we have insulated garage and heat it to 38F with a Rinnai heater. Can I effectively put an interior model tankless or tanked (direct vent) hot water heater in the garage? There is not a ton of room upstairs, and I'd much rather a water mess happen in the garage if there was a failure. There are freeze drain out mechanisms available that could save me if the Rinnai failed.

 

[tcrimsonk]

Thinking out loud here:

Are you planning on having any other plumbing fixtures in the garage area? If not, I'd keep the water heater in the apartment, just in case you have a heat failure in the garage. If you already have other plumbing in the garage, I don't see the harm in putting the heater there too. I'd be sure to insulate the hot water pipes, since the air around them will be so cold. If nothing else, so the hot water makes it to the fixture faster.

In fact, I think I'd insulate all of the plumbing in the garage. Pipe insulation isn't all that expensive. Just because the area around the thermostat is 38, doesn't mean that a pipe running through a cabinet where there's no air flow to your heated environment, that backs up against an exterior wall won't drop below 32.

I'm curious to hear what kinds of pricing you get for Roxul/Drywall vs spray foam for your garage walls. Also, what made you decide on closed cell vs open?

 

[pcampbell]

In the garage, i'd probably just have a hot and cold faucet, maybe a utility sink. I hadn't even thought of that, but hey, might as well!

I believe closed cell is a safer choice for cold climates because it doesn't require a vapor barrier.

 

[yeldogt]

I would foam the walls and be done with it -- end of all your problems. And with a fully foamed building you will find that it will be easy to get warm above what your intended temp is. 36 is cold ... you can't have any plumbing in an area that cold when it gets down in single digits ... especially the WH. I can heat 1700sf into the 60's with a few hundred gallons of propane.

 

[tcrimsonk]

I've been researching spray foam too, I've found the same reason to use closed cell from everyone EXCEPT for the company that actually gave me a quote. (which is frustrating)

Anyway, to your question, I did happen across this:
http://www.greenbuildingadvisor.com...mal-barriers-and-ignition-barriers-spray-foam

It looks like some spray foams are fire rated for use in attics, but if I read this correctly, no spray foam is approved for use in occupied areas unless it's covered. This seems to differ by location and by whether they actually enforce it.

The red flag that I saw for you using it in a garage: “When exposed to fire sources, such as trash fires, welding arcs, cutting torches, or red-hot metal, unprotected SPF [spray polyurethane foam] can ignite and may result in a flash fire.”

There's some more info on page 3 here: http://www.icc-es.org/News/Articles/AY126ThermalBarriersSPF2011-51811.pdf

I guess the real question at that point is, who is going to be living in the apartment?

 

[pcampbell]

I would foam the walls and be done with it -- end of all your problems. And with a fully foamed building you will find that it will be easy to get warm above what your intended temp is. 36 is cold ... you can't have any plumbing in an area that cold when it gets down in single digits ... especially the WH. I can heat 1700sf into the 60's with a few hundred gallons of propane.

Thanks for the advice. Maybe not worth trying to keep it so cold. I was thinking I should still foam the garage ceiling (floor of the apartment), which gives me the option to keep them at different temps... but it will add to the cost quite a bit.

 

[tcrimsonk]

Thanks for the advice. Maybe not worth trying to keep it so cold. I was thinking I should still foam the garage ceiling (floor of the apartment), which gives me the option to keep them at different temps... but it will add to the cost quite a bit.

See if you can find any soundproofing ratings for the spray foam. (I've never looked for it.) You may find that you prefer the roxul, if for no other reason than blocking noise from the garage into the apartment.

 

[pcampbell]

I wonder if the garage does not house any vehicles, gasoline, paint, oil, flammables, etc. Do I still need drywall separating the garage and apartment? It is a significant expense and I'm trying to figure out if I can still rent it out from time to time without it.

 

[HoosierBuddy]

I wonder if the garage does not house any vehicles, gasoline, paint, oil, flammables, etc. Do I still need drywall separating the garage and apartment? It is a significant expense and I'm trying to figure out if I can still rent it out from time to time without it.

If it's got overhead doors, I would think that it has to meet garage code regardless of your future plans. If it doesn't have overhead doors...then it's not a garage. It's just a large hobby room to me.

If you're going to have plumbing in the downstairs anyway...then I wouldn't see a downside to having the water heater down there.

I've got a utility sink in my garage, and use it quite often.

Phil

 

[Bretny]

What ever plumbing you put in the garage make sure you put a low point drain on it. Some day you may not want or have the ability to heat it. Keeping it only a few degrees over freezing makes it quicker to freeze.

 

[James-W]

Living space above a garage, especially if it is living space that you rent out, may have some stringent requirements in your municipality. I would get with the building department and ask a bunch of questions before doing anything else. It is always best to be fully informed going in rather than find out later on that things aren't the way you thought they were.