[Greenbuilding] Windows - double hung

Thu Aug 2 22:17:39 EDT 2007

Life, and buildings are a grand compromise. And every situation is 
different. Particular climates require various solutions. I like double hung 
windows for our situation, at least on some areas of a structure.

Our summer degree days are more demanding than our winter ones, by just a 
little and seemingly increasing. The Fibertec windows we installed in our 
own new home last year vary in style, mostly double hungs with some 
casements and awnings... each serving their own task. The double hungs 
appear to have a pretty good seal in the closed mode, clearly not that of a 
casement but I'm not going to split hairs here. Ever try to use a casement 
to ventilate in a rainstorm? A double hung with a closed bottom sash and an 
open top where there is a modest overhang above (like we design in for such 
reasons as this and summer solar shading) does a fine job of venting in a 
rain storm, or when one is threatening and no one is around to close the 
windows if such occurs. The alternative is mechanical cooling around here. 
Which one is the greener alternative?

There are many days here where (if properly insulated, shaded, and vented) 
mechanical cooling is not required. The ability to open both the top and 
bottom sash of a double hung window provides unsurpassed venting 
capabilities in climates such as ours. I am continually amazed how people 
with double hungs only operate the bottom sash, then when things get 
uncomfortable they close the whole thing and head to the thermostat when 
simply pulling the top sash down would greatly improve the interior 
conditions. Seems folks have forgotten some of the very basic laws of 
thermodynamics, or perhaps never learned them in the first place.

As for the screen shading the glazing issue and reducing solar gains... take 
the screen out in the winter months, as folks have done for decades. They 
will last you about three times longer that way too. And the screen helps 
shade the window in the summer months. How green is that? Pardon me, but the 
main argument that the screen reduces the utility of double hungs is plain 
silly. Take the darn things out when you need the heat and leave them in 
when you don't. But that's just my humble opinion.

Ron Cascio
Chestnut Creek
Design/Build/Consult/Develop
Maryland's Eastern Shore

----- Original Message ----- 
From: "Keith Winston" <keith at earthsunenergy.com>
To: "Greenbuilder list" <greenbuilding at listserv.repp.org>
Sent: Thursday, August 02, 2007 4:02 PM
Subject: Re: [Greenbuilding] Windows - double hung

> Hi And welcome John (and hi Laren):
>
> That's a good article you linked to, John. Does a nice clear job of
> spelling out shortcomings of double-hung (I'd never thought about the
> double-sided exposure of the bottom edge of the upper sash issue, for
> example).
>
> And thanks for the addendum Laren, like so many things its one of those
> things (window screens) that I knew all the information but hadn't put
> it together and considered implications in a consistent way. Thanks for
> helping me do so.
>
> Warmly, Keith
>
>
> LarenCorie wrote:
>> From: "John E. Beeson" <jbeeson at quinnevans.com>
>>
>>
>>> does anyone recommend a manufacturer that makes a good
>>> double-hung?
>>>
>>> And yes, I read this already, but I'm trying to match the historic
>>> windows:
>>> http://www.thermotechfiberglass.com/Column3.htm
>>>
>>
>> Hello John;
>>
>>   There is another factor, that virtually all of the window
>> manufacturers, and the article above, miss, which makes
>> all sliding and hung windows even less energy inefficient,
>> compared to hinged windows.   It has to do with Solar
>> gain, and has been left out of every claim of Solar trans-
>> mittance, I have seen from a manufacturer. First, sliding
>> windows are set deeper in their jambs, so they receive
>> less sunlight at higher angles of incident. This might not
>> be very important, except for the second, far more
>> important factor.   All of the sliding windows put their
>> screening on the exterior, where it blocks 15-20% of
>> the sunlight, from ever getting to the glass. The screens
>> also reduce the opening size, leaving much of the sun-
>> -light to just shine on the sill, or jambs, outside of the
>> actual  window.     You will not see this mentioned in
>> any of the manufacturer's literature, and if you mention
>> it to any of the window sales people (this can be fun,
>> and even profitable, if you turn it into a question and
>> a bet ;O), they will hear something they never thought
>> about before.  However, in any heating climates, like
>> here in Michigan it is a very important factor.  In the
>> Ann Arbor area, south facing windows should gain
>> more heat than they lose, every month, except may-
>> -be December. They should reduce the heating bills.
>> However,  when you stop 30% of your Solar gain,
>> by placing a screen a few inches out in front of the
>> glass, you are definitely not being green.    Hinged
>> windows place their screens inside, where they do
>> not shade the glass.   This is a critical factor on all
>> exposures, except north. In southern states, where
>> cooling is a greater factor than heating, you will
>> do better with double hungs, because of their
>> shading screens, and operable top sashes.
>>
>> -Laren Corie-
>> Natural Solar Building Designs, Since 1975
>> www.LarenCorie.com
>>
>> -LittleHouses- http://groups.yahoo.com/group/LittleHouses
>> -Energy Self-Sufficiency Newsletter- Free at  www.rebelwolf.com
>> -WoodGas- Power from Wood. http://groups.yahoo.com/group/WoodGas
>> -Refrigerator Alternatives-
>> http://groups.yahoo.com/group/RefrigeratorAlternatives
>>
>>
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>
> -- 
> Keith Winston
> Earth Sun Energy Systems
> Hyattsville, MD 20781
> 301-980-6325
> send me mail at
> keith at the company below
> www.EarthSunEnergy.com
>
>
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