need solution to heat attic separately

[earthworks]

I'm just starting framing on my 32 x 40 garage with attic trusses. The walls are 2x6 with r20 insulation and the attic ceiling will be r30. knee walls will also be r20. I ran the gas line the other day, but haven't decided on the heating source i'll be using.

I'd like to do it the least expensive way. I want to heat the attic which will be my Office / Man Cave to a constant 10C or 15C (21C is 72F that's all i know!), then bring up the temp when i use it. And I'd like to keep the main garage which will be used for parking, just above freezing, or possibly leave it unheated and have storage for things that can freeze in the heated space upstairs. But I do want something to heat the downstairs occassionally. Wood heat would be awesome as i have alot of wood on my property, but too much work to maintain a constant temperature with.

My thoughts are...

- old high efficiency gas furnace can be found used for cheap, and just heat the whole thing, but then have to pay for ducting and worry about an old furnace breaking down. Also they say that parking in a heated garage is bad for the vehicle with all the freezing and thawing of road salts and such. Is this really an issue?

- heat downstairs with hanging unit heater kept very low, and then need a secondary heater upstairs like a gas fireplace

- find a easy solution for heat upstairs, such as a gas fireplace which can also be found cheap used. and then heat downstairs only occassionally with a wood stove

The last option poses the question about insulating the attic floor also, which is another expense and more work. Would it be ok to heat just the attic if it's floor wasn't insulated.

I'm looking forward to your ideas. I've been tossing this around in my head for a while now... these are the things that keep me up at night.

 

[astroracer]

My office (where I am right now) is set up as you are thinking. I heat the upstairs with a small forced air furnace. The "garage" is also heated but the ducts have shut-offs (registers) so most of the heat goes upstairs. If I want more heat in the garage I just open a few of the registers. Right now it's 68 up here and about 50 in the garage. I've been using the office since 1997 and it works just fine.
My floor is not insulated. And it sure is nice getting a warm, ice free car in the morning... Never had one fall apart because of the warm gagrage...
Mark

 

[astroracer]

We used "loft" trusses in this build. The garage is 26 x 28 and the loft trusses give me 14' of usable space upstairs. The knee walls I used for built in storage and book cases.
Mark

 

[p_mori7]

Would you consider some vents between the parking area and the loft area ?

Keeping the garage at 40* should keep the office warmer (probably 50*-ish)

You could then have a seperate 2000W or 3000W 240V heater with fan in the loft for when you are going to work up there.

 

[earthworks]

I thought about ducting to both and restricting flow to the lower floor. My furnace guy said that would kill a high efficiency furnace.
I also was wondering about putting ceiling vents. Butand just heating the lower portion. But then i became concerned with exhaust to the upper floor and dust etc. Especially if it is a semi-living space.
Also gas is much cheaper to run then hydro.

 

[Rockhead261]

Nothing to add, but this thread title reminded me of something funny.

My somewhat paranoid and quite batty great aunt was concerned about the summer heat in her unfinished attic. She asked me if I could air condition it. I told her that was unnecessary and suggested simply adding ventilation. She pressed on, saying she's afraid it would catch fire. I laughed and told her I'd been in some pretty damn hot attics and I've never heard of one spontaneously combusting. She replied, "I'm not worried about spontaneous combustion, I'm worried about it catching fire."

 

[astroracer]

I thought about ducting to both and restricting flow to the lower floor. My furnace guy said that would kill a high efficiency furnace.

Hmm, nothing was said to me about this. Been running the furnace for nearly 18 yrs with no issues... Of course we put in more registers upstairs then there are in the garage so the furnace gets to push as much air as it needs to. The gargage registers are open just a bit so there is flow thru them.
Mark

 

[earthworks]

well eighteen years is pretty good... maybe i shouldn't worry then!

 

[volleyball]

Have you heard of zoning? You get a system that can easily handle the upstairs, you should oversize as you will be not keeping it constantly warm. You set the downstairs to whatever and it will most likely be constant unless you have a project.
1 furnace, two or more temps. I installed a 4 zone valve as it was little more than a 2 zone and I have the option of adding zones as I may want/need.

 

[earthworks]

what kind of furnace is it? forced air gas? I know you can run zones in a radiant system. but haven't heard of this type.

 

[volleyball]

You can zone air or water systems. I was referring to an air system. System works very well.

 

[earthworks]

I found a stand alone wall type forced air gas heater direct vent on kijiji. 50000btu for only $120. If i installed this in the garage do you think it would heat the attic sufficiently also? The stairway will be open and no insulation in the attic floor.
Or what about the opposite? Installing it in the attic. But then im sure id have too much heat upstairs and not enough down.
Also.... is 50000btu enough for the whole garage? Again its 32 x 40 plus a 12 x 40 attic. 2x6 construction. Insulated w/ r19 in walls and r50 in upper attic.
Ive done the btu calculators on the net but none really take in to account the thermal dynamics of two stories and heater location.
Should i go buy that heater?

 

[theoldwizard1]

So what are you going to do for cooling in the summer ?

Not cheap, but a mini-split heat pump is the way to go. Make sure to check the specs and see that it can put out 100% down to least -20C

 

[DEnd]

First of all you need to make sure you air seal between the garage and the office well. Since you will be heating the office the stack effect will draw in air from the garage into the office, so that air seal is critical to keep pollutants out of the office space. That probably also means a wall and door at the stair.

Secondly consider running the roof deck insulation all the way down to the garage walls instead of to the knee wall. This way is much easier to air seal. If you insist on insulating the knee wall read this article and do it properly: http://www.projectwarm.org/res/uploads/media/insulating_kneewalls_fine_homebuilding.pdf

Thirdly, I would go ahead and insulate the floor as well, as there will be some heat loss through the floor otherwise. Insulation ain't that expensive.

Fourthly since this will be "Living" space you should not in anyway connect the attic space to the garage space with HVAC equipment. You want to separate the air between the spaces as much as possible. For a 12x40 attic with good air sealing I would not run any ducting in it anyway, and use a point source for heat, such as a direct vent wall furnace. If you want to heat the garage some too you can put a larger one down there. They are a fairly easy retrofit, so it's not something you have to do now.

Fifthly, if you do a really good job air sealing the attic you will need to add some ventilation in. Since it is above a garage I would use a supply only ventilation system. I would do something like a small bath fan wired to run when the lights are on only vented backwards, and drawing outside air through a filter.

 

[earthworks]

I'm not worried about cooling, we are in a zone where heating is the primary requirement. And we have regular temps below -20C so with the size of my garage, I don't believe the mini-split could meet my requirements. In fact, I don't think any HVAC contractors in our area even know what that type of system is. However after doing intensive research during the construction of my home, I became fairly versed in different heating methods. I almost went with geothermal for my home... but the same sizing and temp differentials were too restrictive, and the cost of electricity in our region made it not a financially viable option. I have a friend who installed it at an immense cost, and his hydro bills are now several hundred a month.. more then my gas bills, and I heat, and cook with natural gas.

 

[earthworks]

As far as air sealing, I had planned an open stairway with no door. and my air barrier plan was to run poly on the vertical garage walls, horizontally across the ceiling which will terminate beneath the knee wall at a 2" xps piece of blocking. the blocking will be spray foamed between the bottom cords of the trusses and stick up high enough that it can work as backing between the knee walls' drywall. this is so that I can seal to it in order to drywall the upstairs using the Airtight Drywall Approach. so it should be as tight as a garage can get considering there are three overhead doors and four windows and two man doors.
I do plan to keep a hazardous materials storage container on the main floor of the garage which will keep noxious fumes to a minimum, and had actually planned to setup a relay system to run an exhaust vent fan for a period of time after each overhead door operation.

do you think I will still require the separation between the two zones? Upstairs will be basically an office for my business and a rec-room for me to hide away from the wife and kids occasionally.

If you read post #12 you'll notice that I had found a 50000btu wall type direct vent heater for cheap. budget and ease of install are two big factors for me... so I was kinda counting on the stack effect heating the upstairs if the furnace was down.
as for cooling, a window at each end upstairs will keep the air fresh and cool up there.

 

[earthworks]

Thirdly, I would go ahead and insulate the floor as well, as there will be some heat loss through the floor otherwise. Insulation ain't that expensive.

My insulation for this garage was quoted at $2700 for just fiberglass batting, r19 walls and r38 attic. and I'm a contractor so I get really good prices. I think the price differential between Canada and the US is much greater then many of you realize.

excellent link to insulating the knee wall by the way. I've actually used much of Martin and GBA's technical info to develop many of the details I used in the construction of my home, and will be using in the construction of the garage. to a lesser extent thought in the garage. for cost and time saving reasons. thanks,

 

[DEnd]

do you think I will still require the separation between the two zones? Upstairs will be basically an office for my business and a rec-room for me to hide away from the wife and kids occasionally.

It depends on your local building codes, and how your building inspector classifies the space. If it is classified as storage then you don't need the separation. However since you are using it as living space it really needs to have air separation and have appropriate fire separation of the spaces (with a good escape path). It would **** to fall asleep in front of a movie (or something) and have a fire break out in the garage and not be able to get out in time. For air sealing read this: http://arkansasenergy.org/business_...ow Attached Garages Poison Our Indoor Air.pdf That is for CO, I have read similar studies on Benzene, there as also many other pollutants from garages that can enter living spaces and a hazardous materials storage container is not going to keep those pollutants out of the living space.

As for the insulation cost you spend that money up front so that you don't have to keep spending it for years on heating bills. So how do you want to spend your money, now or every time you have to pay your gas bill? If your building inspector determines that the attic is living space it will probably be required anyway.

 

[earthworks]

Our inspection on accessory building construction is limited to framing inspection so i dont have to meet any other requirements aside from utilities. Ill check out your link re: air sealing
As i said though. I was wondering about the heater in the lower area being enough to heat both the upper and lower spaces. If im heating only one space with a proper envelope disregarding seperate zones for now. Although i imagine your concerns are legit.

 

[volleyball]

I would think that having a door to the upstairs a good thing. If you don't insulate the mancave floor or do very little, heat will radiate into the garage. But if it is truly a parking only garage, it won't hurt to have a duct or two go downstairs, just not a return.
My basement used to be comfortable even without any heat on until I insulated the upstairs floor. I had to stop as it was getting too cold down there in late winter. Since it is a walkout, I don't get the warm ground radiating heat in, just cold air sucking it out.
A lot like having a garage under it.

 

[bzinsky]

I think I have a really good way of, it's exactly what's in my garage and love it. Just use a gas forced hot air furnace. Have one single exposed duct that goes up to the ceiling, and just runs exposed down the middle, end to end. Just cutout holes in it, screw in some standard cheapo vents, and your done. It's really the greatest solution for garage heat because the heaters themselves aren't that expensive. You want a lot of BTU's because you're not maintaining heat, you want a cold place to be a warm place on demand. There's aren't many other solutions that can give you the same btu's for the $. You can do the ductwork yourself, because it's exposed and there are no branches, just a straight duct. Would be perfect for a mancave actually. Just do that industrial theme a lot of retailers have going on. Most of the time I see them using round ducts and painted flat black, totally exposed in some nice looking places.

You don't even really need a return duct, my return duct is like 4 feet long and it just comes out the bottom and curves straight up and is totally open, just a filter at the base. The only reason I even have a return duct is so it doesn't **** up leaves off the basement floor.

Also, I'd just put one big heater in the first floor. Keeping the attic warm means it's almost pointless to keep the lower portion cold. Heat rises, and the most important space to be insulated to keep heat in is above it. If you keep your office at a constant 60 degrees, that means the space between your attic and garage has an R value of infinite.

In other words, if your attic is already heated, the room beneath it would need a ridiculous low amount of btu's to maintain a nice temperature. I've had heatload calcs done on an apartment buildings. The top floor apartment always needs about 3x the amount of btu's as

My best advice is to insulate roof very well, do not insulate office floor, run simple main trunk on garage ceiling, just put a bunch of air vents in between your office and your garage so that the heat created from the garage can just rise upwards. Like a lot of air vents, or maybe even a couple transfer fans. You can set your t-stat in your garage for like 50, and it'd probably make your office slightly warmer.

It's all really simple and cheap, and you can have plenty of heat on demand. No need to wait for a wood burning stove to heat up, that would take hours to warm that place up.

Would it be higher reoccuring cost to heating both places at a given temp? yes slightly higher, but that is completely offset by the simplicity and cost of design, and because you're using one big heater, it will probably allow you to maintain a lower temperature. Who cares if your office is at 45 degrees if it only takes 15 minutes to get to 65 degrees.

Also use a wifi t-stat, so when you need to go into your office, you can turn your heat on from your phone in advance. This will allow you to maintain an even lower temperature when not in use. The maintaining of the temp is the real money killer over time.

Don't use electronic ignition, mine has it, it's super reliable but it takes slightly longer to fire up than a pilot. Every minute is important when you want heat right now. I keep mine off, so I'm sitting there in frustration for 5 minutes waiting for that damn thing to start blowing hot air.

I'd go around 150k btu's

 

[dave67fd]

You should close off (insulate) both areas. Heat each one with it's own heat or zone them.

You said you wan't to do it the least expensive way...short term or long term?

The cheaper you do it the colder and less safe you will be.