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-   -   Basement HVAC room question (http://www.diychatroom.com/f17/basement-hvac-room-question-156396/)

andybeck 09-10-2012 09:58 AM

Basement HVAC room question
 
Hello,

I am in the final stages of finishing my basement and have a question about the ventilation to the room where my HVAC and water heater is located. I have been told that the door to this room needs to be louvered however, with the costs that I have found for louvered doors, I was wondering if there are other options. The room is about 200-250 square feet and is framed/drywalled on two sides and poured concrete foundation on the other two sides. The room as well as the basement is half-below grade so the foundation wall comes up about 50" and has exterior framing above it to the ceiling.

Does a room this size need to have a louvered door?

Is is acceptable to purchase a solid core pre hung door and cut out a section at the bottom where I would add a louver or a nice wood HVAC return vent?

Thanks for your help!

Andy

GBrackins 09-10-2012 02:24 PM

what is the fuel source for your water heater?

andybeck 09-10-2012 02:32 PM

The water heater and furnace are gas fed.

Beepster 09-10-2012 03:25 PM

Is this a normal residential home? Do you have a cold air return to your HVAC room, or anywhere else to your house?

B

GBrackins 09-10-2012 03:37 PM

you need makeup air for gas fired appliances, and as beepster said you need return air.

talk with your hvac guy and see if you can do something different than the louvered door

andybeck 09-10-2012 03:43 PM

There are several returns throughout the house including one that I added in the basement. The home is a typical residential 2-story home of about 2200 square feet.

GBrackins 09-10-2012 04:26 PM

ok so you've gotten the return air, you still need makeup air for gas fired appliances. maybe your hvac guy can installed vents with fresh air intakes. if you do not have sufficient fresh air your gas fired appliances will begin to produce carbon monoxide and when the 02 level is low enough they will be extinguished.

Missouri Bound 09-10-2012 04:33 PM

A rule of thumb is 1 sq. in. per 1000 btu. Add the total btu's of both pieces of equipment and use a grill in the door. Outside air would be a plus!

bobinphx 09-11-2012 09:24 AM

Fresh air intakes through an air to air heat exchanger would be what I would do. I would seal up the room and make it a cold zone. But please be careful!!!! you can really get into trouble fast with CO2 in the house air. Get a pro to design the fresh air feeds and then, if need be, you could install it all.

Missouri Bound 09-11-2012 06:15 PM

Quote:

Originally Posted by bobinphx (Post 1007658)
Fresh air intakes through an air to air heat exchanger would be what I would do. I would seal up the room and make it a cold zone. But please be careful!!!! you can really get into trouble fast with CO2 in the house air. Get a pro to design the fresh air feeds and then, if need be, you could install it all.

Bob....your advice, as written makes no sense at all. You cannot seal up a furnace room....ever.The furnace, and in this situation the water heater as well require combustion air. An air to air heat exchanger is not for that purpose. It is, and I am sure you know it, is for exchanging stale air for fresh air. These are two completelly different situations. Whether the gas burning appliances get combustion air from outside or from within the home, it still needs to have an adequate supply. Sealing up that room is not an answer.

andybeck 09-12-2012 07:35 AM

Thanks everyone for your help!

Bob - I appreciate your advice, feasible or not, however I am trying to avoid the $300 expense of a louvered door. I can't imagine that having an HVAC tech consult and design anything, would be less than the cost of a louvered door.

Missouri - I do not know off hand how many btu's the units are. They are what was installed when the home when it was built in 2004 and are nothing special. Contractor's grade units I believe. I want to say the furnace is a Lennox system but I am not positive. The home is about 2200 square feet, 3200 including the basement.

If I was to cut out a 14x10 space in a hollow core door and fill it with a return air grille, would this be enough ventilation for most residential systems? According to your formula, this would provide for 140,000 btu's. I will check the btu's on the systems, I am just wondering if you can give me a ballpark guess as to what they might be.

Thanks!

Andy

Missouri Bound 09-12-2012 08:49 AM

Those are the proper calculations, sq in per btu. But keep in mind that a grill can only supply 75% of it's actual dimension due to framing and louver placement. So...a 14 X 10 grill will be adequate for 105 cu in. Easy enough to determine your grill size using a 75% factor. :thumbsup: The btu information will be on the name plates of both the water heater and the furnace.

bobinphx 09-12-2012 09:23 AM

Quote:

Originally Posted by Missouri Bound (Post 1007977)
Bob....your advice, as written makes no sense at all. You cannot seal up a furnace room....ever.The furnace, and in this situation the water heater as well require combustion air. An air to air heat exchanger is not for that purpose. It is, and I am sure you know it, is for exchanging stale air for fresh air. These are two completelly different situations. Whether the gas burning appliances get combustion air from outside or from within the home, it still needs to have an adequate supply. Sealing up that room is not an answer.


I totally defer to your expertise!!! I have seen this done many times in the midwest, so I was going from experiance. Just so that everyone that reads this has a better idea, I have some questions.

1. is this a code issue??
2. sort of a MFGR combustion inlet, what is the best way to plumb in fresh air for combustion
3. is there a formula for BTU/effency/ volume of air needed? (sort of like a mnaual j or d ??)

thanks in advance and sorry to sort of hijack the thread.

beenthere 09-12-2012 03:27 PM

By code, if you use a grille in your door, you would need 2 grilles, one within 12" of the floor, and one within 12" of the ceiling.

Marty S. 09-12-2012 05:31 PM

And those grills have to connect the furnace room with a space large enough to get the required combustion air. For example the basement was divided into a furnace room,2 bedrooms , a hall way and a game room. Combustion air can't come from a bedroom so only the hall area,furnace room and game room would get counted,and that's if there's no door to the game room. If those three didn't meet the 50 cubic feet of free air per 1000 btu minimum then there would need to be grills at the door at the top of the stairs too.

Bob the minimum required combustion air from inside the house is calculated with the 50 cubic feet of free air per 1000 btu (water heater and furnace combined). I don't remember the exact formula for bringing in outside air for combustion but the rule of thumb was not less than half the volume of the flue so a 5" flue would need a 4" pipe from outside. We had to tee that so one end was within 12" of the ceiling and the other end was within 12" of the floor. Made for some mighty cold furnace rooms when winter temps dipped way below zero.


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