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Finishing Basement - Question on HVAC requirements


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#1 JFT Ben

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Posted 11 February 2010 - 02:17 PM

We're finishing our basement, and have the framing done. Nothing too fancy, a bedroom, large rec room (maybe 450 sf) and bathroom along with storage space. I have no idea on what is required for HVAC by code and what is recommended. Basement (unfinished) is typically comfortable temperature year round, but needs dehumidifier running in summer.

We have supply and return in the bedroom, which is located beneath the main spine of the furnace duct run. No worries there.

We'll put in an exhaust fan in the 1/2 bathroom, does it need forced air/return? It's right by the main trunk, so wouldn't be too bad if we had to do that.

The rec room: There is for sure one supply branch stubbed out on the main duct run, so we'll run it out to the far exterior wall. Not sure on the air return/intake. Do we need one, and if so, where does it get placed (higher right? and accross from the supply?) Is one air supply/intake going to be enough in that size room? Is there a code requirement per SF how much you would need, esp. in a basement?

I obviously have no idea, so am looking for a little help. The other stuff we have covered.



#2 St. Louis Bob

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Posted 11 February 2010 - 03:08 PM

PM Otis, he has a guy.

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#3 GTBilly

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Posted 11 February 2010 - 03:12 PM

Your basement should have the necessary vents already in the ceiling or running down walls. Check and see and just use those after you modify them to your needs.
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#4 boofatty

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Posted 11 February 2010 - 06:55 PM

1. Do not put a return in the bathroom. You should put forced air vent in the room to heat/cool. On the return, think about it for a second, the return pulls air from that room and redistributes throughout the rest of the house. Do you want bathroom air recirculating? Stick with the exhaust fan. I'm assuming the half bath is small, so it may not even need a supply vent. but you may want a louver in the door or wall to allow warm air from other rooms to heat the half bath.

2. Generally placement of supply vs. return air in homes is kind of an art, and can depend on layout, type of system, etc. you don't want them too close together. Look through the rest of your house for ideas.

3. the quantity and size of returns mostly affects how your machine will operate, how many times per hour it recycles the air in a room. you should look at the manual, or the mfr website for their recommendations. Most will pull local air (air from directly in front of the unit) and the return duct is simply to recycle the air from a room.

As a general basement finishing note, my friend used to be a home appraiser and told me that your basement should match the other floors of your house in terms of quality of finishes. It will be appraised a flat rate, regardless of what you spent on the basement. For the basement to get full appraisal value equal to the other floors, it must have central heat and air to be considered livable space. I always thought that was the best advice I ever rec'd. Of course, now the market is crap.

#5 Jack Burton

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Posted 11 February 2010 - 07:30 PM

Boofatty is right, dont put a return in the 1/2 bath. Personally I would put in a small baseboard electric heater in the bathroom instead of a supply vent because when you think about it how much time do you really spend in there anyhow?

Your return air for the rec room should roughly match whats upstairs and the bedroom return is usually the space between the bottom of the door and the floor.

Put supply air vents lower, beneath windows is preferable. You want to try and create an envelope by sealing off areas where the heat loss/gain is the greatest.

Put return vents as close to main return trunk as possible. Less duct and turns equals less static.

Typical rule of thumb air requirements:
A/C 450 cfm per ton

#6 jon_mx

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Posted 11 February 2010 - 07:39 PM

1. Do not put a return in the bathroom. You should put forced air vent in the room to heat/cool. On the return, think about it for a second, the return pulls air from that room and redistributes throughout the rest of the house. Do you want bathroom air recirculating? Stick with the exhaust fan. I'm assuming the half bath is small, so it may not even need a supply vent. but you may want a louver in the door or wall to allow warm air from other rooms to heat the half bath.2. Generally placement of supply vs. return air in homes is kind of an art, and can depend on layout, type of system, etc. you don't want them too close together. Look through the rest of your house for ideas.3. the quantity and size of returns mostly affects how your machine will operate, how many times per hour it recycles the air in a room. you should look at the manual, or the mfr website for their recommendations. Most will pull local air (air from directly in front of the unit) and the return duct is simply to recycle the air from a room.As a general basement finishing note, my friend used to be a home appraiser and told me that your basement should match the other floors of your house in terms of quality of finishes. It will be appraised a flat rate, regardless of what you spent on the basement. For the basement to get full appraisal value equal to the other floors, it must have central heat and air to be considered livable space. I always thought that was the best advice I ever rec'd. Of course, now the market is crap.

I have never seen an appraisal that appraises the basement the same as the rest of the house. The costs are not that much different (a basement maybe 10-15% cheaper), but appraisers around here usually appraise the basement significantly less.

#7 boofatty

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Posted 12 February 2010 - 08:29 AM


1. Do not put a return in the bathroom. You should put forced air vent in the room to heat/cool. On the return, think about it for a second, the return pulls air from that room and redistributes throughout the rest of the house. Do you want bathroom air recirculating? Stick with the exhaust fan. I'm assuming the half bath is small, so it may not even need a supply vent. but you may want a louver in the door or wall to allow warm air from other rooms to heat the half bath.

2. Generally placement of supply vs. return air in homes is kind of an art, and can depend on layout, type of system, etc. you don't want them too close together. Look through the rest of your house for ideas.

3. the quantity and size of returns mostly affects how your machine will operate, how many times per hour it recycles the air in a room. you should look at the manual, or the mfr website for their recommendations. Most will pull local air (air from directly in front of the unit) and the return duct is simply to recycle the air from a room.

As a general basement finishing note, my friend used to be a home appraiser and told me that your basement should match the other floors of your house in terms of quality of finishes. It will be appraised a flat rate, regardless of what you spent on the basement. For the basement to get full appraisal value equal to the other floors, it must have central heat and air to be considered livable space. I always thought that was the best advice I ever rec'd. Of course, now the market is crap.

I have never seen an appraisal that appraises the basement the same as the rest of the house. The costs are not that much different (a basement maybe 10-15% cheaper), but appraisers around here usually appraise the basement significantly less.

I hear ya, my friend used to appraise around the ATL area. I talked to him today and he clarified that the most you can get appraised for your basement is what the value of your upper levels receive. So if my first and second floors get $80/SF, then the most my basement gets is $80/SF; and this is largely dependent on the heat and cool capabilities of the basement, among many other things (is it a daylight basemement, has its own egress, etc). He mentioned this to me becauase he had several home owners that went overboard on basement finishing with putting very nice finishes in the basement (marble or granite, etc) which led to a finishing cost of let's say $100/SF. The owners were mad when it only appraised at say $80/Sf because the rest of their house was not as nice as the basement. The point is don't turn your basement into a cathedral if the rest of your house is just a church, you will lose money.

He had also told me that the basement HVAC is one of the most important aspects to an appraiser. Without a dedicated central heat and air unit for the basement, it would likely be appraised at a lesser value. A shared HVAC is not the same due to lack of true control from the basement. It must have heat and air to be considered complete. There are ways to add local control to a shared HVAC, just need the right parts.

#8 JFT Ben

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Posted 12 February 2010 - 09:05 AM

He had also told me that the basement HVAC is one of the most important aspects to an appraiser. Without a dedicated central heat and air unit for the basement, it would likely be appraised at a lesser value. A shared HVAC is not the same due to lack of true control from the basement. It must have heat and air to be considered complete. There are ways to add local control to a shared HVAC, just need the right parts.

Awesome info, thanks guys. A friend of ours did their basement and did a large forced air space heater type thing integrated into their wall with it's own controls. Obviously doesn't impact AC, and not a centralized heating unit, but it seems to work at heating part of the room.

A really dumb, basic question: is basement HVAC a matter of comfort (and subsequently higher appraisal for doing it "right") or is it required by code for defined living spaces?

#9 boofatty

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Posted 12 February 2010 - 10:05 AM


He had also told me that the basement HVAC is one of the most important aspects to an appraiser. Without a dedicated central heat and air unit for the basement, it would likely be appraised at a lesser value. A shared HVAC is not the same due to lack of true control from the basement. It must have heat and air to be considered complete. There are ways to add local control to a shared HVAC, just need the right parts.

Awesome info, thanks guys. A friend of ours did their basement and did a large forced air space heater type thing integrated into their wall with it's own controls. Obviously doesn't impact AC, and not a centralized heating unit, but it seems to work at heating part of the room.

A really dumb, basic question: is basement HVAC a matter of comfort (and subsequently higher appraisal for doing it "right") or is it required by code for defined living spaces?

Its been a long time since i read the residential code, but I'm near positive for it to qualify as livable space it does need heat and cooling, otherwise its still just a fancy basement. Another thing brought by appraiser friend and RE agent, if you filed for permits and it was inspected by city and met code, it should garner higher value than a project done without permits, inspections, etc. The paper trail involved with the city adds legitimacy. Not everyone files their permits on basement jobs, or pass inspection, even though they should. Of course I should add that all this advice was given to me at the height of the market.

I'm just holding on until the right time to sell, hopefully in the next 5-10 yrs or so.




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