Any body out there with HRV experience? My house is being built with an unfinished loft above the garage which shares a wall with, but is separate from the house, and accessed via stairs from inside the garage. It’s at the taping stage.
The loft has one suction for the HRV, in the future bathroom, but no return. Other areas in the house have both. This doesn’t seem quite right to me, especially above a garage where the negative pressure in the loft will tend to suck fumes into the loft, but my builder says that the makeup air will be drawn in from outside through small seams and cracks (!?). Seems to defeat the whole purpose of having an HRV, but HRV’s are new to him, and maybe to his sub installer too. At the time the ducts were installed the loft had an opening to the house (a “door”) for easy movement of materials. I think the HRV installer may have thought that the two would remain connected and instead of correcting it now by installing another duct (more work now because the drywall is up)(but even more work later!) just wants to convince me that it’s OK .
What thinkest ye with some HRV experience?
Thankyou – Brian
Replies
Make him put in the duct!!
That will require tearing up some walls. I'm going to propose to him that an insulated duct be run through the attic which connects the loft to the ceiling of the house. The make-up air will then come from the house itself and with minimal tearing up of walls.
However, if I propose that now, he will have to recoup the cost of doing it by lowering the quality of something somewhere else in the house. I think I will wait until the house is done to propose it as it will be no more work to do it later.
I think this is fair. Anyone disagree?
- Brian.
The loft has one suction for the HRV, in the future bathroom, but no return. Other areas in the house have both. This doesn't seem quite right to me, especially above a garage where the negative pressure in the loft will tend to suck fumes into the loft, but my builder says that the makeup air will be drawn in from outside through small seams and cracks (!?).
So long as the small seams and cracks to the garage are smart enough to know that they aren't supposed to let anything through while the others can, you'll be OK.
Otherwise a really good low level CO monitor will let you know how much CO poisoning you're getting.
I hope it's obvious I think the GC hasn't thought this one through.
_______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11
Bob,
I must be missing something; I didn't think the code allowed any duct openings in the garage. Technically, isn't the loft part of the garage?
What am I missing?
Thanks.
I never met a tool I didn't like!
Nick, I got the impression the loft is above the garage but not part of it; but it is a little hard to tell from the decription.
_______________________
10 .... I have laid the foundation like an expert builder. Now others are building on it. But whoever is building on this foundation must be very careful.
11 For no one can lay any other foundation than the one we already have--Jesus Christ.
1 Corinthians 3:10-11
He says that the loft is accessed via stairs from the garage. Unless the floor and door are built to fire code, wouldn't that make the loft an integral part of the garage, and subject to the code requirement of no duct opening between house and garage?
You're right, it's not entirely clear on the setup, so I'm asking hypothetically. Personally, I think the arrangement is a CO disaster waiting to be broadcast on the evening news. My wife has gotten into the habit of warming up the car in the garage for 10 minutes before driving away, and even with the magnet sealed metal door between the mud room and garage and an open garage door, the fumes can be noticable in the house. Imagine if a fan was pulling from the garage and exhausting into the house while a car was running.
Again, there must be something I don't understand about the setup.
Thanks for the reply.
I never met a tool I didn't like!
My wife has gotten into the habit of warming up the car in the garage for 10 minutes before driving away, and even with the magnet sealed metal door between the mud room and garage and an open garage door, the fumes can be noticable in the house.
So, Nick, does your wife think CO poisoning is cheaper than a divorce? Does she wait in the house too, or outside in the cold, letting the fumes seep into the house while you're in there alone. I hope that you're alone, .. If you have kids, subjecting them to those levels of CO is child abuse. See if you can't get her to at least back the car out onto the driveway, and let it warm up there. Then, there's the belief that warming up a car for ten minutes is about nine minutes too much.
I would suggest that you put your mother-in-law in the added room, then when the fumes are sucked up in the "seams & cracks" you can blame in on the contractor. Usually code requires that the area that seperates the garage and the living space be double layers of of fire rated dw and each layer is to be taped. This is so that fumes cannot get to the living area. If the fumes cannot get there then the make-up air cannot get there. Sounds like a mistake that someone is trying to get out of fixing without billing you!
Actually, there is a self-closing, magnetically-sealed fire door at the top of a fire code-required 5/8" drywall-enclosed stairway. This effectively (at least legally) divides the loft from the garage. The floor of the loft is IFR PEX tubing enclosed in 1 1/2 " of concrete on top of screwed and glued ply subfloor. The ceiling of the garage is FG batt with drywall which hasn't been installed yet because the garage slab hasn't been poured yet.
A 2X6 wall with FG batts and 6 mil poly VB with 5/8" drywall divides the loft from the upper floor of the house.
The make-up duct that I will propose should work nicely because it will be taking air from a high-ceilinged area in the house which would pool warm air (when the ceiling fan is off) in winter and recirculate it into the loft. There is an HRV return duct at this point in the house. If these two ducts in the loft are balanced properly (and I AM assuming competence on the part of my HRV installer) there will be neither significant positive nor negative pressure in the loft relative to the garage below and therefore the CO2 detector should not be activating, even if someone IS trying to commit suicide in the garage!
Regards - Brian.
Thanks for the description. The light in my head went on with the visual.
Thanks again, and good luck with the balancing act.
I never met a tool I didn't like!