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GBlist: Loose windows in South Florida
Beverly,
Sounds like almost ANY change you make will be an improvement over your old
jalousies.... (commonly called "ja-loosies").
First, regarding TIGHTNESS:
In general, windows with bulb-type compression weatherstripping are the
tightest, especially after repeated openings and closings. These are
predominantly used on CASEMENT-type windows. These are also the best at
"catching" prevailing breezes to aid in cooling or venting. Choose windows
that have a tested air leakage value less than 0.1 cfm/sqft or 0.1 cfm/ft of
crack length. Make sure the values are recently tested and certified (either
by AAMA or NWWDA). If certified, the manufacturer will be able to show you a
test report and a certification label on the window.
If you are stuck with sliding or hung windows, again, look for low air
leakage values, labeled and certified.
Second, regarding vinyl outgassing:
While I don't know everything about the U of F study, I do know that not all
plastics are the same and not all "vinyl" is the same. If you want low
maintenance, vinyl-clad or metal-clad are your best option. Check with the
name brand manufacturers of clad windows for specific outgassing data.
Andersen is the largest manufacturer of vinyl clad wood windows. Pella is
the largest manufacturer of aluminum clad wood windows. There are many
others. Metal frames in South Florida have been around for a while and may
be sufficient for your needs, though not as energy efficient. I'd be REAL
cautious about hollow vinyl windows in south Florida. (Anybody know how hot
a south-facing surface gets in the summer there?). As always, check the
warranties and go with a manufacturer that will stand behind their product.
But for your energy concerns about the windows, the glass is everything
there.....
Regarding ENERGY PERFORMANCE:
You want to find windows that provide (1) desired visual clarity with (2)
appropriately low solar heat gain coefficients (SHGCs). The lower the SHGC,
the greater your air conditioning savings. (reducing the soal heat gain
contribution to the cooling load).
There are lots of glazing options that are designed to reduce solar gains....
many are tinted or colored. BEWARE! Just because a glass is tinted or
colored does not necessarily mean it is good at rejecting solar gains! Some
of these glazings are good absorbers! My choice would be to find one of the
"spectrally selective" low-e coatings that provides a very low SHGC while
maintaining a good visual clarity. These are enclosed in an insulated glass
(IG) unit to protect the coating. Both Cardinal Glass and PPG make coatings
of this type. All of the major manufacturers have these glazing options.
(If you don't mind a little tint, there are also some low-e coatings
designed to reject even more solar gain with a slight loss of visible
transmittance.)
Look for SHGCs less than 0.35 in South Florida. Then decide how clear you
want your glass to be. Again, look for NFRC ratings and labels to be sure
you are getting the cooling savings you desire.
Changing your old windows, with improvements in both air leakage and solar
control, should dramatically impact your comfort and air conditioning bills.
!!!!Please let the list know what decision you make and what changes/savings
result.!!!!
Good Luck!
Chris Mathis
MCSquared
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