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jmejiaa 01-28-2011 11:25 PM

Automatic vent close/open for furnace room?
We are int he process of re-doing the basement. Everything is pretty much done and sealed off and we have an issue.

The architect put vents from the furnace room the the exterior of the home, these were installed and insulated by the contractor and the inspector approved it before closing it up completely. We recently had a couple of days where it was about -5 degrees and I noticed the water in some pipes froze, mainly the upstairs shower drain and some downstairs pipes.

We haven't had a day like this again but for now I covered the vent with insulation(I know this is a no no but the vent has never been there in the first place with the same setup so I figure I'll be good until I find a solution or it get a bit warmer, 1-2 weeks tops).

I've spoken to the contractor and he tells me everything was done right, which I saw was all insulated, the city inspector has also been very strict and he actually made them insulate the vents more prior to closing up and giving us the OK. So as much as I would like to say this is a mistake on their(contractor) part I honestly don't think it was.

I have asked the contractor to please take the vent cover off as I want to see if there is any non insulated space between the pipes and outside(circular pipe, rectangular opening)

Sorry for the lengthy post, what I am looking for is some sort of vent grill that can open and close either based on temperature of the furnace operating. I know they exist, but the opening is a rectangular one... I would not mind paying for this and having a good solution(not closing it up during coldest winter weeks).

having it open/close also minimizes the cold air coming in or hot air in the summer.

Something like this looks like something I would use but I was thinking if they exist with some insulation, as I am sure the cold will get through pretty quick with this setup:

Picture of the setup, this is from the blueprint:

Marty S. 01-29-2011 08:54 AM

That's the oxygen supply for your gas burning furnace and water heater, called combustion air. Clean burning appliances with enough air produce very little carbon monoxide and it goes out the flue pipe. Sealing the room and closing that air will quickly depleat the oxygen in that room when the fires burn. Fires burning with not enough oxygen produce a TON of carbon monoxide,levels well above all safety and legal limits. Once the oxygen get low enough the gasses waft out the face of the burners instead of going out the flue.

Your options are to replace the water heater and furnace with direct vent ones or leave the combustion air duct open. You could replace just the water heater with a direct vent and then a mechanical damper could be put in the combustion air duct. The damper would be interlocked with the furnace so it could not run if the damper failed to open. Replacing both appliances and sealing that big hole letting -5 degree air in the home is the cheapest option in the long run but the the highest up front cost. Not what you wanted to hear but that's the way it is.

yuri 01-29-2011 09:24 AM

Marty is correct. How old is the house and furnace and water heater. Both need replacing at some time and it may be better to do it sooner than later. You have to spend money to save money but in the long run a high efficiency furnace will pay for itself with fuel savings. A rectangular motorized damper and interlocking controls and wiring is going to be expensive and can break down and leave you w/o heat.

jmejiaa 01-29-2011 09:40 AM

The house is from the 70s. We just bought it as ourfirst place and were pretty much forced to do the basement over as it was done illegally initially.

definitely not what I wanted to hear :(.

For now I will leave it open, we will look into appliances. Would it be just the furnace or does the water heater need to change as well. The bad part is the ducks are there and they took a good amount of room in the laundry room but then we can close out the exterior hole.

yuri 01-29-2011 10:07 AM

Water heaters are less than 35,000 BTUs and mostly the gas code allows you to use them w/o a combustion air duct/pipe as most homes leak enough air in for combustion. If you seal the furnace room too tight or your local code requires combustion air then you have to have it. Most of the time we change over to an electric water heater here and that eliminates the chimney and air loss/$$ flowing up it 24 hrs a day and saves you money.

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