On inefficient windows | By Umbra Fisk | Grist | Ask Umbra

On inefficient windows

08 Nov 2006

Got questions about the environment? Ask Umbra.

Dear Umbra,

I am lucky enough to have a home I really love and food to feed my family and my pets. However, the home has one major energy flaw: it is older and has huge, single-pane window/walls with aluminum frames, in two adjoining rooms. We currently are not able to replace them, and they lose heat rapidly. With this winter being a bit colder, is there anything that you can suggest we do, other than the window upgrades we cannot afford, to keep some warmth in the house?

Justine
Concord, Calif.

Ask Umbra continues below

ADVERTISING POLICY

Dearest Justine,

That sounds very chilly to be sure. I can't pity you too much -- at least you live in Concord, Calif., and not one of the other Concords -- but if you think you're cold, I believe you. Three winterization actions may help your situation: caulking, curtains, and storm windows. Weather-stripping is not an option for you with fixed-pane glass, so we'll talk about that in another column.

Improving efficiency doesn't have to be a pane.

Photo: iStockphoto

Take a little gander over at the Efficient Windows Collaborative site I mentioned in my last column to get an idea of how much money you will save in your climate when you replace your inefficient windows. That at least will help you plan toward window replacement, which is warranted with your conductive aluminum windows.

To dispense with curtains: the idea is simply that heavy curtains drawn over the windows at night have an insulating effect. New curtains can be expensive, but you can hang up blankets if you have extras.

To find out if caulking will be helpful, check the seal on your windows. You can do this by lighting a candle or incense stick, then passing it around all the edges where they meet your house. As you see the flame or smoke quiver less and more, you'll learn a bit about how well the original installation caulking is holding up over time, and where the drafts are. (A windy day would help -- and don't set anything on fire.) If you find drafts, it is simple and inexpensive to reseal them with caulk. Ask for tips at the hardware store if you've never caulked, and you'll avoid mass piles of goop.

Your windows are single pane, aka single glazed; double glazing is much better for warding off heat loss and gain. Since you can't afford new, all-in-one, double-glazed windows with triple-e coating and argon and blah, blah, blah right now, storm windows are another way to achieve double glazing. Even the cheap plastic adhered with tape strips and a blow dryer is a sort of double glazing. That would be the most economical, and it is effective. Next step is to build or buy reusable storm windows.

A fixed-pane storm window is a large piece of plastic or glass encased in a wooden or aluminum frame, which is either permanent or seasonal, interior or exterior. It'll fit into the window and stick in place with little toggles or hinges. Important components will be an excellent fit and weep holes at the bottom for condensation to exit if it is an exterior window. It should be airtight itself, or what's the point? The Energy Efficiency and Renewable Energy guide at the Department of Energy has more to say on this point, and the American Council for an Energy-Efficient Economy does too (they won't have you settle for an air leakage rate higher than 0.3 cfm/ft -- 0.3 cubic feet per minute of air leakage per linear foot of window edge).

You can make storm windows yourself or buy them from another, and only you can make that decision. I'm not handy enough to make something square. If you are, various DIY websites or homebuilding magazine archives will have instructions -- but, I repeat, I'm not handy enough to evaluate and recommend one.

I've been trying to figure out for myself how storm windows stack up against entirely new windows. Apparently they don't particularly help with insulative properties, but do stop airflow; one public utility claims they provide a 25 to 50 percent reduction in heat loss during the winter. Sounds good to me, and hopefully affordable to you.

Caulky,
Umbra

Yours is to wonder why, hers is to answer (or try). Please send Umbra any nagging question pertaining to the environment -- but first check out her FAQs!

The claims made in this column may not reflect the views of this magazine. Neither the magazine nor the author guarantees that any advice contained in this column is wise or safe. Please use this column at your own risk.

Umbra Fisk is Grist Research Associate II, Hardcover and Periodicals Unit, floors 2B-4B.

Comments: (4 comments)

You are not logged in. Thus, you cannot post a comment. If you have a Gristmill account, log in below. If you don't have a Gristmill account, well, by all means go make one! Meet you back here in five.

Cold Windows

I too live in a realtively mild CA climate and own a very old home. It took me several years to have enough money to replace the large original plate glass windows in my living room. (3 windows two 3.5 and a 5x5)with wooden frames! I couldn't be in my living room for 4 months of the year without looking like an Eskimo. Plus it was noisy as I live on a busy street. I found a company that installs replacement windows that are double pane with low e and one pane that is 3/16th" thick. The extra thickness is terrific in blocking noise. The replacement windows do not require you to remove any exterior trim, provided your existing windows are not surface nailed to begin with. Simply remove the stops on the inside, remove old, replace with new and replace wood stops. Whoalla! New warm quiet windows in about an hour. Suddenly my heat bills plummeted and I could lounge in my T-shirt in the living room in the dead of "winter."

It might be worth it to take out a small line of credit or loan to do the replacements and see the heat and or cooling savings help pay off the loan! Check locally to see if there is a "Homeworks" or similar company that advertizes "replacement" windows. I was so thrilled I replaced all my office windows (1920's bungalow)and had the same wonderful results.

A caveat here, the only actually affordable windows other than leaky aluminum ones are made out of vinyl. I know that Umbra would never use them, but please consider they are made in a more environmentally responsible manner now in the US and will last basically forever, which is a good thing. The key is a "thermal block" between inside and outside which vinyl and wood can easily do. Problem is that wood windows are many times more expensive for us mere mortals.

PS, Plastic with tape and or storm windows will not come close to helping solve this problem.

K. Austin, Architect

K. Austin

by Kathy Austin at 12:53 PM on 08 Nov 2006

new not necessarily better

From NPS preservation brief 9:

Many styles of storm windows are available to improve the thermal performance of existing windows. The use of exterior storm windows should be investigated whenever feasible because they are thermally efficient, cost-effective, reversible, and allow the retention of original windows (see "Preservation Briefs: 3"). Storm window frames may be made of wood, aluminum, vinyl, or plastic; however, the use of unfinished aluminum storms should be avoided. The visual impact of storms may be minimized by selecting colors which match existing trim color. Arched top storms are available for windows with special shapes. Although interior storm windows appear to offer an attractive option for achieving double glazing with minimal visual impact, the potential for damaging condensation problems must be addressed. Moisture which becomes trapped between the layers of glazing can condense on the colder, outer prime window, potentially leading to deterioration. The correct approach to using interior storms is to create a seal on the interior storm while allowing some ventilation around the prime window. In actual practice, the creation of such a durable, airtight seal is difficult.

...

Consider energy efficiency as one of the factors for replacements, but do not let it dominate the issue. Energy conservation is no excuse for the wholesale destruction of historic windows which can be made thermally efficient by historically and aesthetically acceptable means. In fact, a historic wooden window with a high quality storm window added should thermally outperform a new double-glazed metal window which does not have thermal breaks (insulation between the inner and outer frames intended to break the path of heat flow). This occurs because the wood has far better insulating value than the metal, and in addition many historic windows have high ratios of wood to glass, thus reducing the area of highest heat transfer. One measure of heat transfer is the U-value, the number of Btu's per hour transferred through a square foot of material. When comparing thermal performance, the lower the U-value the better the performance. According to ASHRAE 1977 Fundamentals, the U-values for single glazed wooden windows range from 0.88 to 0.99. The addition of a storm window should reduce these figures to a range of 0.44 to 0.49. A non-thermal break, double-glazed metal window has a U-value of about 0.6.

(emphasis added)

by willa at 6:20 AM on 09 Nov 2006

Chilly Screens of Winter

We live in a 115 year old house in Denver, CO. I can testify that rehabbing the original wood windows and adding good quality storm windows are great ways to reduce heat loss through the windows. We are gradually rehabbing the existing windows (replacing cracked panes, new caulk, weatherstripping, ensuring tight fit) and are getting new storms (wood frames with exchangeble screen/glass panels) made. The temperature (and noise) control in the rooms that have rehabbed windows is very noticably improved compared to those rooms yet to be done. Plus, the look is wonderful -- very compatible with the historic appearance of our house. I can't speak to price comparisons -- we never considered replacing the windows due to their historic nature.

by kellya at 1:03 PM on 14 Nov 2006

High Windows

I lived in a victorian house for nearly twenty years. The main ground floor reception rooms all had huge expanses of glass in the original wooden frames. When we moved in we found that the previous owners had fitted large sheets of glass which acted as crude secondary double glazing. These were removeable for the summer months. After we moved on the house was converted into flats and new replacement windows fitted throughout.

Hugh

by Hugh H at 7:12 AM on 17 Nov 2006

The comments of Grist users reflect the opinions of those individuals only, and do not necessarily reflect the viewpoints of Grist, its staff, its board members, their psychotherapists, or their aestheticians. Got it?