walling in mechanicals during basement finish


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Old 01-23-11, 08:51 AM
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walling in mechanicals during basement finish

I've been reading some threads concerning air flow to furnaces, etc.

We're going to start finishing our basement. All our mechanicals (furnace, hot water heater, sump, etc) are along one wall and I'd like to frame a wall to separate them from the rest of the space. I'd like to insulate the finished area.

The house is 3 years old and the furnace draws air from outside. I should also add that what will become the mechanical room has an opening to the crawlspace.

Here are my questions:

Should I worry about allowing air into the mechanical space (via, for example, a vent in the door?).

Are there any problems with insulating the ceilings in the finished area?
 
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Old 01-23-11, 12:39 PM
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I don't have the numbers at hand, but there are size and clearance requirements for the mechanical room which are related to the size of your system. Whether that requirement changes with a sealed combustion system needs to be checked.

You say your furnace draws from the outside, but is it a sealed system? If not a true sealed system, there are other concerns.

Is your hot water a combustion appliance and if so how is it vented and supplied with air?

Forced hot air systems have another problem, pressure balancing. If the supply air is greater than the return capability, then your furnace will find a way to draw in more air. If any of your supply air is leaking to the outside, then again the furnace will pull in outside air to replace it. Your dryer, bath fans, kitchen fans, and any other exhaust appliances will all compete for inside air and need to be considered in the worst case condition. Extremely large fans, like whole house fans and indoor grills, can over power many exhaust appliances. If you have any, their needs need to be reviewed.

With the current open area, your furnace has access to a lot of air. But, enclose it, and you need to be careful.

Next, insulating and finishing your basement. There are guidelines that can help avoid some of the typical problems down the road. When you are ready to start, open another thread for advice.

Bud
 
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Old 01-30-11, 08:07 AM
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Sorry for the delay in responding, bud9051. Thanks for your reply.

Best as I can tell, the furnace is a true sealed system. I can make sure before we start the job, but it looks totally sealed up. No obvious places where it seems to be open to the basement.

the water heater is gas- so I guess its a combustion appliance. Supply and vent are both to the outside (via a blower - I suppose since its so far from the outside wall).

Are those numbers you're refering to size and clearance for mechanical rooms local code? Set by furnace manufacturer? I.e. - where do I look them up?

I'm hoping that the roughly 5'X5' opening to the crawlspace - right above the furnace and water heater - will take care of most of the concerns you mentioned.

In any event, it looks like I should consult the company that installed our system. I'll talk to the guy when he comes in a few months for the spring check-up.

Thanks,
 
 

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