Results 1 to 11 of 11
  1. #1

    HVAC for basement

    Hello all,

    I am working on finishing my basement and was hoping to get a little bit of clarification on the HVAC. The basement HVAC was completed by the originally home builder, but I just want to make sure the install is acceptable once the basement is finished.

    House is located in Wichita, KS and was built in 2010. Upstairs is 1200 sq ft and open to the basement which will be 900 sq ft with family room, 2 bedrooms and bathroom. Basement is completely below grade with 8 ft ceilings. There is a Ruud 80% furnace rated at 75,000 BTU and a hot water heater rated at 40,000 BTU.There are 6 3x8 supply runs with one to each room and 3 to the family room.

    Return air questions:
    There is only one 14 x 14 return air vent in the basement ceiling currently located about 8 ft from the furance room.

    1) My understanding is that return air vents should be at least 10 feet away from combustion sources. My plan is to move this down the hallway another 10 feet so it is located at the edge of the family room and about 20 ft away from the furnace.

    2) Is only one return air vent for the whole basemenet ok? I wanted to add returns to each bedroom, but I have floor trusses that are very full near the utility area and this would be very difficult without adding any bulkheads.

    Combustion Air
    3)According to the builder's foreman there plan was to have me add grills to the furnace room door (when it gets installed) to provide indoor combustion air. From my readings I am concerned that my house is considered a "unusually tight construction" since it was built in 2010. I do have a 5" fresh air line going straight into the return vent near the furnace. I understand that fresh air and combustion air are different, but I didn't know if maybe this makes my house not be unusually tight.

    4) We are also hoping to add a ventless fireplace to the basement at some point in the future and while our house has enough cu ft according to the calculations I just have an uneasy feeling about these systems and was wondering if anyone has had any problems with them.

    Sorry for the long post and thanks in advance for your help.

  2. #2
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159

    Brian,

    Quote Originally Posted by Brian L View Post
    Hello all,

    I am working on finishing my basement and was hoping to get a little bit of clarification on the HVAC. The basement HVAC was completed by the originally home builder, but I just want to make sure the install is acceptable once the basement is finished.
    Does this space have egress according to the Code, so you can get out in case of fire?
    House is located in Wichita, KS and was built in 2010. Upstairs is 1200 sq ft and open to the basement which will be 900 sq ft with family room, 2 bedrooms and bathroom. Basement is completely below grade with 8 ft ceilings. There is a Ruud 80% furnace rated at 75,000 BTU and a hot water heater rated at 40,000 BTUin the basement right?.There are 6 3x8 supply runs with one to each room and 3 to the family room.

    Return air questions:
    There is only one 14 x 14 return air vent in the basement ceiling currently located about 8 ft from the furance room.
    I question the return in the basement, you have enough return leakage down there already, you don't want the space going negative pressure
    1) My understanding is that return air vents should be at least 10 feet away from combustion sources. My plan is to move this down the hallway another 10 feet so it is located at the edge of the family room and about 20 ft away from the furnace. see above

    2) Is only one return air vent for the whole basemenet ok? I wanted to add returns to each bedroom, but I have floor trusses that are very full near the utility area and this would be very difficult without adding any bulkheads.

    Combustion Air
    3)According to the builder's foreman there plan was to have me add grills to the furnace room door (when it gets installed) to provide indoor combustion air. From my readings I am concerned that my house is considered a "unusually tight construction" since it was built in 2010. I do have a 5" fresh air line going straight into the return vent near the furnace. I understand that fresh air and combustion air are different, but I didn't know if maybe this makes my house not be unusually tight. If you are really concerned that the house is tight then how about a Tegerland (spelling ) fan for combustion air

    4) We are also hoping to add a ventless fireplace to the basement at some point in the future and while our house has enough cu ft according to the calculations I just have an uneasy feeling about these systems and was wondering if anyone has had any problems with them.
    Now this is where you really have combustion air concerns, Hopefully Hearthman will add his opinion

    Sorry for the long post and thanks in advance for your help.
    Good Luck You need to understand more and better yet get a good contractor who raises these kinds of concerns then you'll know you're not just getting someone who simply is doing what you told them to do
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,065
    Quote Originally Posted by Brian L View Post
    Hello all,

    IReturn air questions:


    Combustion Air
    3)According to the builder's foreman there plan was to have me add grills to the furnace room door (when it gets installed) to provide indoor combustion air. From my readings I am concerned that my house is considered a "unusually tight construction" since it was built in 2010. I do have a 5" fresh air line going straight into the return vent near the furnace. I understand that fresh air and combustion air are different, but I didn't know if maybe this makes my house not be unusually tight.

    4) We are also hoping to add a ventless fireplace to the basement at some point in the future and while our house has enough cu ft according to the calculations I just have an uneasy feeling about these systems and was wondering if anyone has had any problems with them.

    Sorry for the long post and thanks in advance for your help.
    You need mechanical fresh make-air to provide the ASHRAE recommended 70 cfm of fresh air at a minimum when occupied to purge indoor pollutants and renew oxygen. The exhaust devices and ventless fireplaces need the make-up to function. Because of your location in a green grass climate, use a whole house ventilating dehumidifier to provide controlled, filtered, fresh air when needed. These units also will provide <50%RH during cool damp weather and high outdoor dew points.
    I like the Ultra-Aire whdehu. There are others.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #4
    In response to Genduct's questions yes there is an egress window in one of the bedrooms. The second bedroom is techincally an office and will be used as a toy room.

    The hot water heater is located in the basement right next to the furnace.

    I guess I am not understanding this part of your response.

    "I question the return in the basement, you have enough return leakage down there already, you don't want the space going negative pressure"

    What do you mean by return leakage down there and are you suggesting that I close off the one return in the basement and not have any?

    Also is it just best to put in an outside combustion air source? I could just but a little J hook in the pipe at the bottom to try to not get too much cold air into the house. I am trying to not spend too much money on most of my solutions as we will only be in this house for another 4 years which limits our time to makeup any costs on energy efficency.

    thanks again

  5. #5
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,383
    Re.
    Quote Originally Posted by Brian L View Post
    4) We are also hoping to add a ventless fireplace to the basement at some point in the future and while our house has enough cu ft according to the calculations I just have an uneasy feeling about these systems and was wondering if anyone has had any problems with them.
    You are right to be concerned about the "ventless" fireplace. The term "ventless" is very misleading. Burning a fossil fuel WILL generate combustion byproducts. A "ventless" fireplace merely dumps these byproducts into your living space. You run the risk of moisture and resulting mildew, not to mention oxygen depletion and possible carbon monoxide poisoning. Since your house is tight you need to consider from where your combustion air will come and how you will dispose of those combustion byproducts. A much safer alternative is a direct vent heater which both brings in air for combustion from outside and discharges the vent fumes to the outside.

  6. #6
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Quote Originally Posted by Brian L View Post
    Combustion Air
    3)According to the builder's foreman there plan was to have me add grills to the furnace room door (when it gets installed) to provide indoor combustion air. From my readings I am concerned that my house is considered a "unusually tight construction" since it was built in 2010. I do have a 5" fresh air line going straight into the return vent near the furnace. I understand that fresh air and combustion air are different, but I didn't know if maybe this makes my house not be unusually tight.

    .
    Sometimes yes, sometimes not. Same with old houses beign leaky. That's not always completely true either. It depends if good construction practices were used and how many corners were cut. Al contractors cut some corners. Has it been tested for it's air leakage rate? If it's really that tight, you may need some ventilation added.. or as mentioned, at least fresh air for the HWT and furnace. IF it's that tight, you won;t need humidificaiton in the winter and may liekly need ot dehumidify it by using ventilation in winter.

    Also factor in that bath fans and a clother dryer can make a space slightly negative.

  7. #7
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159

    To answer your question

    Quote Originally Posted by Brian L View Post
    In response to Genduct's questions yes there is an egress window in one of the bedrooms. The second bedroom is techincally an office and will be used as a toy room.

    The hot water heater is located in the basement right next to the furnace.

    I guess I am not understanding this part of your response.

    "I question the return in the basement, you have enough return leakage down there already, you don't want the space going negative pressure"
    What do you mean by return leakage down there and are you suggesting that I close off the one return in the basement and not have any?

    Negative pressure in relation to outside will pull flue gas so that is a problem. The return duct typically is not sealed and therefore you already have som de facto return even without the grill ( which I suggest you seal


    Also is it just best to put in an outside combustion air source? I could just but a little J hook in the pipe at the bottom to try to not get too much cold air into the house. I am trying to not spend too much money on most of my solutions as we will only be in this house for another 4 years which limits our time to makeup any costs on energy efficency.
    You go to all te trouble of sealing up yopur home only to allow holes to exist? there is a power supply fan that will bring in combustion air when the furnace runs if you think you are too tight
    thanks again
    I'll try to get the right spelling for the fan Compny

    http://tjernlund.com/combustionairintake.htm
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  8. #8
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,046
    TJERNLUND

  9. #9
    Join Date
    Jul 2001
    Location
    Central MN and the Twin Cities
    Posts
    1,530
    JUST SAY NO TO VENTLESS!!!!!

    Say yes to multiple returns located by the floor, not one in the ceiling and say yes to a combustion air to the mech room floor.
    Warning: Just because I am over the head injury doesn't mean I'm normal!

    The day I stop learning.... I'm dead!

  10. #10
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,046
    As long as your mechanical room will be open to the rest of the house you should be fine. I high and low transfer grill in the wall of the mechanical room should be sufficient.

  11. #11
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    If your supplies are in the ceiling blowing down towards the floor, don't get too worried about where the returns are. For a bsement, near the floor is nice, but i wouldn't tear walls down to get one there... and wouldn't put it on a cold exterior wall either. Try and get the suppleis near the perimeter walls and the return ner the center of the room.

    In my last house, ti was easy because the supply branches for the main floor were between the floor joists, so it was a simple matter to either tie into those branches or run a new branch form the main trunk. Some branches had too much airflwo anyway and were dampered quite a bit so it made sense to just put a T on those.

    I agree also, don't get ventless. You life is potentially dependant on a $5 oxygen sensor.... probably made by the lowest bidder in Pakistan or China.

    My inlaws installed one on their fireplace against my recommendations. I can smell when they have it on the moment I enter the house. Fortunately it's a leaky 1960's home, and being smokers, in the whole scheme of things a little elevated CO or CO2 levels is the least of their worries.
    Last edited by motoguy128; 12-20-2011 at 09:52 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event