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  1. #1
    Join Date
    Jul 2008
    Posts
    26

    Question Design Stage HVAC Questions

    Hi,

    I have a couple of questions on how to proceed with our new house. We are going to build a 2,100 sf (main floor) ranch with a walkout basement, which will be heated and cooled with a heat pump, ground sourced if we can afford it. Half of the basement will be unfinished.

    The house will have 9 foot ceilings on both levels. We are considering changing the basement to an 8 foot dropped ceiling, but leaving the wall height as is in order to increase the mechanical space above the ceiling.

    Our architect does not include any HVAC detail in his plans, other than space for the mechanical equipment. He includes everything else. We have yet to select a GC, so we don't know who the possible HVAC subs might be.

    My questions:

    The preliminary drawings we have on hand show the mechanical equipment in a storage room at one end of the finished basement. I would rather it be installed in the unfinished portion of the basement and against the rear wall. Is this a bad or good idea.

    The floor plan is very open, and I am concerned that the HVAC contractor, whoever he is, might have problems locating places to put the return air ducts and registers that don't interfere with our living plans. I am assuming the supply registers will be in the floor, but I would prefer them to be elsewhere. What are my options in this regard? Is using the wall cavities for the returns a good idea? A lot of small returns might work better for us than a two or three large wall grills. Where should the supply and return registers be ideally located, high or low?

    Basically, I am trying to gain knowledge to better discuss our HVAC options with our GC and his HVAC sub.

    Thank you for taking the time to read this.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,320
    You can have the equipment at the unfinnished side.

    Floor supplies work much better then wall supplies in combination heating and cooling installations.

    Using wall cavities for returns, you will have a lot of them weather large or small. You can't get much return through a wall cavity.

    Have returns installed each bedroom, then a floor return somewhoere in the main open area in a corner.
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  3. #3
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    It would help if we knew what part of the country you are building in.

    Floor or low wall registers work better up North, ceiling or high wall registers work better in the south.

    The decision to go geothermal is also dependent on climate.

    My duct work is in my unfinished basement with wall stacks putting the supply registers a few inches below the ceiling. It works well, but it is labor intensive.

    If the unfinished part of the basement is still conditioned space, then there is nothing intrinsically wrong with putting the air handler there.

  4. #4
    Join Date
    Jul 2008
    Posts
    26
    Sorry about the missing location. I had that in there, and then managed to lose it in editing. It's East Tennessee, in the Tennessee Valley.

  5. #5
    Join Date
    Jun 2008
    Posts
    80
    Definitely go with what these guys are saying about returns.

    Since your ceiling will be a little higher than norm and this is a new install, make sure whoever sizes the system takes that into account, along with your wall, ceiling, and floor insulation; exterior type; roofing; windows and doors types and sizes. I presume at this point you have a good handle on all that, so it may be possible to size a system now.

    There seems to be many posts on this forum about contractors not running the calculations and over or under-sizing units for customers.

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,535
    Any interest in fresh air ventilation and IAQ? 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"

  7. #7
    Join Date
    Jul 2008
    Posts
    26
    Yes.

  8. #8
    Join Date
    Jul 2008
    Posts
    26
    Forgot to add that we will be installing a wood stove and hope to do a lot of the heating with that, provided I am still able to cut and split wood as time goes on.

  9. #9
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by Frog_Pond View Post
    Forgot to add that we will be installing a wood stove and hope to do a lot of the heating with that, provided I am still able to cut and split wood as time goes on.
    Think pellet! The new ones are sweet: high-eighties efficiency, easy install with no need for chimney - just vent outside, electric start, thermostatic control of auger and built-in blower, minimum clearances, large hopper, little mess, and btu cost of fuel is comparable to wood.

    Of course if you want to heat yourself multiple times (splitting, stacking, carrying, and burning), wood is the way to go.

    Upfront cost is steeper, but if I had to do it all over that's the way I'd go!

    Just my $.02

  10. #10
    Join Date
    Aug 2006
    Location
    Dallas (Plano), TX
    Posts
    168
    Quote Originally Posted by Frog_Pond View Post

    The house will have 9 foot ceilings on both levels.

    The preliminary drawings we have on hand show the mechanical equipment in a storage room at one end of the finished basement. I would rather it be installed in the unfinished portion of the basement and against the rear wall.

    Is using the wall cavities for the returns a good idea?
    I recommend you consider going up another foot for the main level, to 10' ceilings, especially if you have an open floor plan. The illusion of a much more dramatic living area is heightened just with the extra foot.

    We have a very open floor plan for our living areas, found the incremental expense to go from 9' to 10' ceilings not to be substantial, and thankfully have said repeatedly how pleased we are with that decision.

    Ideally you would located the HVAC mechanical equipment in the center of the home to maximize the performance of the air distribution system. If this isn't possible while still keeping it in conditioned air, you may want to consider putting the equipment in the attic to get optimum air distribution performance.

    I learned last year how difficult it is to have air returns not leak badly when they are built using the between-stud-cavities behind the drywall. Regardless of where you put them, I recommend the returns be pipe that's been sealed well with mastic. We had all of our between-stud-cavity returns replaced last year with returns to the ceiling. Not ideal placement for cooling, but, certainly allowed for a very tight air distribution system.

    Best regards,

    Bill

  11. #11
    Join Date
    Jun 2008
    Posts
    80
    Quote Originally Posted by a0128958 View Post
    Ideally you would located the HVAC mechanical equipment in the center of the home to maximize the performance of the air distribution system.
    Agreed. That also minimizes duct runs having numerous benefits.

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,535
    I hope this is not too extreme for you. I suggest 50 cubic feet of fresh make-up air when the home is occupied. This help a wood stove chiminey work and avoid smoke being sucked into the home when you open the stove to load in wood. Bath fans, kitchen hood, and clothes drier need make-up to function. Fresh air purges indoor pollutants and renew oxygen. During cold weather, fresh dry air removes extra moisture. During spring, summer, and fall, fresh air contains extra moisture that must be controlled. At the peak cooling, the a/c will maintain <50%RH which important for comfort and controlling mold/dust mites. During wet cool weather, supplemental dehumidification is required to maintain <50%RH. If you have not been following the IAQ post, a ventilating whole house dehumidifier can be used to provide fresh dry when the home is occupied. They filter, blend the fresh air with house air, circulate the blended air throughout the home using the ducts of the a/c. There will be more comments from others I am sure. 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"

  13. #13
    Join Date
    Jul 2008
    Posts
    26
    Thank you, Teddy Bear. We will keep that in mind.

    I don't think anybody could convince me to install HVAC in the attic. I don't like out of sight, out of mind. If I can't glance at the equipment every day or so, I get very unhappy. I prefer happy.

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