Additionally, the NSA recommends considering the external appearance of the sunroom, or how it will fit with your home's architecture.

And if you're thinking about resale value, Remodeling Magazine's 2001 Cost vs. Value Survey says the national average cost of a sunroom is $27,081. You can expect that about 60 percent of that - $16,247 - would be recouped when you sell your house.

"It adds to the value, no doubt," said Fort Worth, Texas, appraiser William Durham. "But the typical buyer might look at it as maybe half as valuable as original living area."

However, real estate agents in some parts of the country reported extremely high rates of return. For example, in Washington, D.C., a $26,751 sunroom is estimated to bring back some $24,400 at the time of sale.

Meanwhile, the NSA also says glass used for sunrooms can include single or double paned windows, Low-E, self-cleaning, tinted/protective coatings, and High Performance Low E2 (a double coating of Low-E glass). Ask what kinds of glass manufacturers offer, because the right glass can cut the cost to heat and cool a year-round sunroom.

According to Energy Star a government-backed program helping businesses and individuals protect the environment through superior energy efficiency, using their windows and doors can help reduce utility bills up to 15 percent. Energy Star products also provide protection against sun damage to fabrics in your home.

Energy Star window performance is based on:

• U-factor: The rate of heat transfer either from your home or the outside through your window, door, or skylight. Lower numbers mean less heat is transferred
• Solar Heat Gain Coefficient: How much heat your house gains from the sun. Lower numbers mean less gain.

The cost of today's sunrooms can run from minimal to more than $50,000 depending on the size, style, site location, and materials used to construct them.

When selecting a sunroom dealer, your primary considerations should be reputation, quality, product line and customer satisfaction. Ask if they are insured and can provide references. As with any project, get at least three bids from qualified contractors.