Ducts in garage

[kurt]

This afternoon's house is concrete slab. All ducts in slab (yeah, I know...).

The attached garage is heated w/2 floor registers, fed by ducts in the slab.

I know about ducts in garages violating separation, return air, furnaces in garage supplying houses, etc., but what about a furnace in the middle of the house supplying the garage through floor registers w/the ducts in the concrete slab?

[jon_ran]

I would say that they are not allowed because it violates the gas-proofing. Should gas spill or a vehicle be left running in the garage, there would be nothing keeping it out of the home.

[Jim Katen]

When the furnace is not running, might it be possible for the house to be depressurized enough to draw garage air into the house?

- Jim Katen, Oregon

[hausdok]

Why wouldn't it be possible to equip the ducts with actuator activated dampers so air can't backflow into the home?

OT - OF!!!

M.

[Richard Moore]

With the system running, assuming there is no return in the garage (which would be very wrong), wouldn't you be creating some positive pressure in the garage and, therefore negative pressure in the house. All the air you manage to pump into the garage will have to be replenished somehow in the house. Even with a good weather-stripped door to the interior and the "firewall" intact, it seems there would inevitably be some transfer through "cracks" from the garage to the interior. And that's no matter where the registers are.

Mike's "actuator activated dampers" sound very fancy but my head says registers in a garage just have to be wrong, doubly so in the floor.

[John Dirks Jr]

Think about it this way. Why do they want you to elevate water heaters with pilot lights in the garage? Because the pilot can ignite combustible gasses that can gather at the floor.

Wouldn't those same gasses be able to sink into the floor registers in the garage and have the potential to be mixed into the air that is distributed in the house?

[kurt]

Interesting. I've stumped the brain trust for a hard reference. I couldn't think of one either.

Except, Jim's and Richards (and sort of AHI's) consideration about pressurization drawing fumes into the house. That's what I hung my opinion on, and no one disagreed, even the realtor (amazing).

Either way, very strange. Never seen anything like it.

And Mr. O', this was a 1947 POS. No actuated dampers in those rusty old registers. Interesting idea, but my head started to explode up when I thought about it. Where can I look at actuator dampers?

Thanx all.

[inspect4u]

Kurt,

If you want a reference, go to IRC R309.1.1. It deals with duct penetration and states there shall be no openings into the garage. I take that to mean, ceiling, wall, or floors.

Mike M

[hausdok]

Hi Kurt,

So, you looked at a 60 year old test bed that hasn't killed anyone. Hmmm. I'm not advocating it, and I know there's probably a prohibition against it somewhere; however, I bet from an engineering standpoint it's not that difficult an issue to lick.

For instance, if the house had an actuator activated makeup air damper for the whole house air change system - and many do - that could be set to activate simultaneously with any dampers between the garage and the house, thus allowing fresh outside air into the system without taking air from the garage, the house and the garage would both be under positive pressure, but the garage, being leakier than the interior as so many are, would allow fumes to leak out under/around the overhead door and at other areas.

Kurt, look at these and check out the positive seal iris damper at the sixth one.

http://www.infolink.com.au/articles/HVA ... 134450.htm

http://www.ductair.com.au/images/pdfs/S ... tuator.pdf

http://www.ventprod.com/catalog/7/55

http://www.ventprod.com/catalog/7/43

http://www.continentalfan.com/resid.htm

http://www.continentalfan.com/iris.htm#iris3

ONE TEAM - ONE FIGHT!!!

Mike

[kurt]

Originally posted by inspect4u

Kurt,

If you want a reference, go to IRC R309.1.1. It deals with duct penetration and states there shall be no openings into the garage. I take that to mean, ceiling, wall, or floors.

Mike M

You know, that's it. Contained right there in the last 7 words of the section.

Thanks.

Mike, what's a "test bed?" And what does it mean that it hasn't killed anyone?

I'm cornfused....

[hausdok]

Hi,

Well, for more 6 decades that house has been an experiment to see whether a duct opening into a garage could result in anyone getting killed. Maybe none of the owners realized it, but now you can tell them that their experiment has concluded that those ducts wouldn't result in anyone having been killed under normal circumstances (As if that will be any real comfort.).

OT - OF!!!

M.

[Jim Katen]

Originally posted by hausdok

Hi,

Well, for more 6 decades that house has been an experiment to see whether a duct opening into a garage could result in anyone getting killed. Maybe none of the owners realized it, but now you can tell them that their experiment has concluded that those ducts wouldn't result in anyone having been killed under normal circumstances (As if that will be any real comfort.).

OT - OF!!!

M.

It isn't normal circumstances that kill people. It's the exceptional circumstances that do it.

- Jim Katen, Oregon

[hausdok]

Originally posted by Jim Katen

Originally posted by hausdok

Hi,

Well, for more 6 decades that house has been an experiment to see whether a duct opening into a garage could result in anyone getting killed. Maybe none of the owners realized it, but now you can tell them that their experiment has concluded that those ducts wouldn't result in anyone having been killed under normal circumstances (As if that will be any real comfort.).

OT - OF!!!

M.

It isn't normal circumstances that kill people. It's the exceptional circumstances that do it.

- Jim Katen, Oregon

Your absolutely right; thus, my use of the word normal.

Don't get me wrong; I'm not advocating it. I just think that technically I bet there's a way that it can be done; not that it's legal to do so.

OT - OF!!!

M.

[Richard Moore]

"Your (tut-tut) absolutely right; thus, my use of the word normal."

The trouble is that it's very difficult to predict that the client's "normal" behaviour would mirror that of the previous owners.

"Don't get me wrong; I'm not advocating it. I just think that technically I bet there's a way that it can be done; not that it's legal to do so."

Can't argue with that. We put a man on the moon after all. But...in order to be both efficient and safe I see no option but to also put a return in the garage so conditioned air doesn't just get blown out the garage door and cold air constantly sucked into the house. That would then require a combination gasoline vapor, CO, heat sensor set to eject the homeowners out of bed and safely to the exterior. I'm pretty sure I saw just the thing on a Wallace and Grommit episode. []

Easier to just seal the register ducts and install a simple garage heater...if they actually need one.

[Brandon Chew]

But...in order to be both efficient and safe I see no option but to also put a return in the garage so conditioned air doesn't just get blown out the garage door and cold air constantly sucked into the house.

Agreed, but then you run into this problem:

§RG2440.5 (§FG617.5) Prohibited sources. Outside or return air for a forced-air heating system shall not be taken from the following locations:

2. Where there is the presence of objectionable odors, fumes or flammable vapors;

5. A closet, bathroom, toilet room, kitchen, garage, mechanical room, boiler room or furnace room.

It isn't normal circumstances that kill people. It's the exceptional circumstances that do it.

Yep, as I was reading down the thread, when I came to your post I was thinking "what happens if there is a fire in the garage?"

Since I can't find anything in the code that says you are required to have a return in the same room as a supply duct, I'd go with IRC §R309.1.1 as was noted above. The supply register is a great big honking opening in the duct in the garage.