[Greenbuilding] New HVAC unit

[Ron Cascio]

I think Bob has some very healthy advice there Bobbi. 

Do the insulation/isolation work first to get the load down, then size the system appropriately. The smaller the better, usually.       

Ron

  ----- Original Message ----- 
  From: Bob Klahn 
  To: Green Building 
  Sent: Wednesday, June 01, 2011 10:10 PM
  Subject: Re: [Greenbuilding] New HVAC unit


  Bobbi,
  I agree that blowing cellulose into the walls and ceiling are your best initial reinsulation options. With caveats.

  1) Blowing the attic can be an easy DIY - assuming that you have good access and that it's all open, flat attic - no kneewalls or "slopes" (the top floor ceiling that follows the rafter line.  If it's a walk-up attic, so much the better.  Is any of it floored for storage?

  2) Prep work to seal all penetrations of the ceiling plane.  This will require digging through/displacing the existing insulation to find them and to get sealing access.  It's labor-intensive, and in that heat best done in the winter or on rainy days.  However, it is essential to avoid losing much of the insulation value you (will have) worked hard for.  (I know of no insulation contractor in this market willing to even consider doing it, even though - or perhaps because - it could easily double the cost of the job.)  After that, adding insulation is easy.

  3) I agree that you would be wise to blow the exterior wall cavities yourself - unless you can find an insulation contractor - and, more critically, installer who is familiar with dense-pack blowing techniques and will include in the contract assurance that all cavities were located and filled- and that all were filled to dense-pack densities.  Offering to verify with an infrared scan, or agreeing to an independent one you contract yourself, is a strong plus.  If they don't offer one, you should find someone who will do one independently.
  If you decide on - or are forced into - doing it yourself, email me; I'll be happy to send instructions or talk you through it.

  4) Look for an Energy Rater in your area, with either RESNET or BPI certification, to run a blower door test on the house to locate the air leaks; a house that age is very likely to have lots and controlling them is critical for controlling comfort, costs, and the mold potential.  The Rater could also do a full analysis to determine what the "design load" (how big an A/C you really need) is - and what it will be after you re-insulate and air tighten.  Ask your HVAC dealer if he ran "ACCA Manuals J, D, and S on the house to determine the size units (condenser and evaporator) you 'need'; the duct sizing and reductions for the proper delivery flows and what the design flows are for each room.  In my experience, most don't; it's too time-consuming so they rely on "rules of thumb".  The only thing the ROT's will guarantee is that you will not get the most efficient installation. 

  Too large an A/C unit will keep you cool, but will not run long enough each time it cycles to adequately dehumidify.  When allergies and mold are concerns, this is critical.  Mold, and a number of other allergen producers just love the elevated humidity...

  I don't know what your cost and completion limitations are, but I always advise clients to plan these upgrades in stages - but never to do something that will have to be undone, or redone, to implement the next stage.  Blowing the walls and adding a layer of wall/insulation can make an expensive job astronomical.  The sheath wall can be added as a later stage.

  There, I've slid into loggaria again.  Sorry,all.  But simple advice can so easily get twisted.  Besides, I avoided cleaning up the kitchen for a bit.  For that, I thank you.



  On 6/1/2011 5:07 PM, Bobbi Chukran wrote: 
    I'll bet he didn't live in Central TX, though.  :-) 

    It was 90 there yesterday, and is supposed to be 100 for most of this week.  Even though that house was built to be cooler *in the time it was built* the climate has changed. 

    There are also health issues to address, such as the high mold counts here and allergies. 

    bobbi c. 

    On Jun 1, 2011, at 2:25 PM, Reuben Deumling wrote: 


      I once had a professor who asserted that the presence of a compressor AC in a house was a sign of poor design. In other words there were (in principle) ways around using AC in all climates>>> 


    _______________________________________________ 
    Greenbuilding mailing list 
    to Send a Message to the list, use the email address 
    Greenbuilding at bioenergylists.org 

    to UNSUBSCRIBE or Change your List Settings use the web page 
    http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org 




------------------------------------------------------------------------------


  _______________________________________________
  Greenbuilding mailing list
  to Send a Message to the list, use the email address
  Greenbuilding at bioenergylists.org

  to UNSUBSCRIBE or Change your List Settings use the web page
  http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org



------------------------------------------------------------------------------



  No virus found in this incoming message.
  Checked by AVG - www.avg.com 
  Version: 9.0.901 / Virus Database: 271.1.1/3674 - Release Date: 06/01/11 12:45:00
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20110602/d6d648a5/attachment.html>