Windowplanningcenter.com Premier Distributor of Windows and Doors to the Carolinas!

A Guide to Energy-Efficient Windows and Doors

Section 2 — How to Get Started

2.1 Assessing Your Situation

As with most projects, the first step is deciding where to begin. When designing a new home you should think seriously about the quality of window that you want to specify. With window improvements, you have to determine what is wrong with the existing units, what your expectations are in upgrading, and how much you want to spend. Some problems can be solved without replacing the entire window.

Figure 1Uncomfortable drafts due to air leakage, for example, may be solved with a combination of new weather stripping, new hardware and sealants. Interior storm windows that fit into, or over, primary window openings are another comfort solution, which adds energy efficiency to an existing window. They are easy to install and remove. Costs of these storms can vary. In some cases, new windows will be required. Many frames are so inefficient, you may wish to replace them too.

2.2 Should You Reglaze, Retrofit, or Replace?

If you're thinking of upgrading existing windows in your client’s home, you have essentially three options. In option 1, let's say you have old, single-pane, double-hung windows in wood frames and sashes. The sashes (the part that moves) and frames (the part the sashes slide in are in good condition, and you want to keep them. So, you decide to reglaze with double-paned, insulated glazing (IG) units which are custom-made to fit into the individual openings (Fig. 1). If the sash isn't thick enough, you may not be able to follow this option. Always check the warranty before making any decision. This option can actually be cost prohibitive and the least energy efficient.Figure 2

In option 2, suppose the sashes are in poor condition, but the perimeter frame is OK. In this case, you decide to retrofit the glazing and sash while keeping the perimeter frame and retaining the same window style (Fig. 2).

In option 3, let's assume the old double-hung window is in such bad shape that nothing is worth saving; even the perimeter frame and trim are in bad shape. In this case, you elect to replace the whole window as a unit—glazing, sashes, frames and all. This gives you the option of changing the style of window, say, from double-hung to vertical casement (Fig. 3).

Figure 3Given these three options, make sure that you and your supplier are talking about the same type of installation.

2.3 Designing with Windows and Doors

The sun's energy is free. Solar energy can improve the lighting and comfort of your home, and it can cut your fuel bills; it can also provide too much warmth and cause overheating, both in summer and winter. Decisions you make at the planning stage about the number of windows, their size and location—particularly in relation to the sun's orientation at different times of the year—will be as important a consideration in determining your window requirements as their insulative properties or how they look.

For example, increasing window areas on the south side of a building can increase the contribution that the sun makes to heating the home in the winter, which may offset your heating costs. But be sure to plan for sufficient eave overhang to shade these south-facing windows in the summer months to prevent unwanted solar gain.

Until recently, an established rule of thumb in window placement was to install fewer and fixed windows on the north side of a home, to prevent excessive heat losses in the winter. Another rule of thumb recommended keeping east and west exposures to a minimum except when needed for aesthetics and daylight, in order to prevent excessive solar heat gain in the summer.

But over the past several years the rules for window placement have been turned on their head by advances in window technology. The arrival of high-performance windows (see Section 7) has given consumers more choice in window selection—whether it's for an existing home renovation or for specifying in a new home.

The old rule of thumb was to keep the ratio of window area to floor area at about 1:10. That is, for every square foot of window area, make sure you have at least ten square feet of floor area. This will prevent overheating in the living space due to too much solar gain when using windows with high shading or solar heat gain coefficients. Standard building code requires clear glass glazed openings not less than 8% of the floor area served by them. Some exceptions do apply.

If you combine traditional passive solar design principles (described in Section 4) with high-performance windows (described in Section 7) you can get much greater net solar gain while reducing your energy consumption for space heating and cooling. In the Piedmont and coastal areas of the Carolinas, passive solar design has taken a back seat to super glass. Excessive heat gain costs more in cooling than is offset in reducing heating costs during the winter. This is why a low SHGC number is recommended.

And remember, doors also play an important part in the energy performance of the home, especially if you have a lot of patio doors. Depending on the condition of existing doors, energy-efficient replacement units may contribute to increased comfort and reduced energy bills. An added bonus of energy-efficient doors is that they tend to be heavier and more robust than conventional doors, thus enhancing the security of the home.

2.4 What to Look for in Windows and Doors

The wide variety of windows and doors available on the market can make the task of selecting appropriate units confusing. Price may not always be the determining factor. The cheapest units you can find may not perform at the level you want. However, some moderately priced units may perform as well as, or even better than, higher-priced models. The best advice to keep in mind is that price is not always an indication of quality or performance.

The cost of energy-efficient, high-performance windows can be 10 to 15 percent more than the standard double-glazed unit. However, many window manufacturers are switching over their entire production line to produce only high-performance units so, in effect, there is no price differential as far as they are concerned. Today, the high-performance window is becoming the industry standard. Read about it in Sections 7 and 8.

But it can still be confusing. For example, some window manufacturers include low-E coatings in their standard windows, with gas fills as an upgrade, at higher cost, while others offer gas fills and special coatings as an upgrade. (See pages 29 to 30 for an explanation of low-E coatings and gas fills.)

Once you've done your homework by reading this guide, you'll be better prepared to ask the right questions when you specify windows and, equally important, know when you're getting the right answers.

The key is to select windows or doors that are as energy-efficient as possible, given your needs and budget. Remember that some super high-performance windows may cost considerably more than normal high-performance windows. The NFRC system and Solar Heat Gain Coefficient described in Section 6 will give you an indication of the energy benefits of these windows. In most cases, the more efficient unit will probably offer other advantages, such as better comfort, increased fabric-fading protection, sound reduction and resistance to condensation in very cold climates.

Don't forget to consider the advantages and disadvantages of framing materials, as well as the maintenance required and the durability of hardware. Windows are a long-term investment.

Inspect samples before making a decision, taking into account the following basic features described in greater detail in this publication:

Window type may be fixed or operable.

Glazing type affects energy efficiency and the amount of light which passes through the window.

Frame materials affect the insulation value, strength, maintenance requirements and longevity of the window.

Energy performance—there may be a trade-off between efficiency and price.

Warranties differ from supplier to supplier and window to window, compare before you purchase.

Next ->

Contact Info.

Email: info@windowplanningcenter.com
Website: windowplanningcenter.com