There’s no simple answer to how to choose the correct windows, but here are some things you should watch for.

Windows serve three purposes: They provide light, airflow and ventilation. But they should also help keep the heat out in the summer and in during the winter. That has to do with R-value — in other words, insulation — and the air-tightness around the window itself.

Every window leaks heat. You can have the best windows on the market — triple-paned, double low-E coatings — but they will not have the same insulation value as an insulated wood or concrete wall; no matter how thermally efficient they are.

The trend today is to increase the size of your windows, not to mention the number of windows in a home. People love natural light. But at the same time we need to make sure the windows are improving the house — not working against it.

Heat loss and gain through windows accounts for about half of our heating and cooling needs. A poorly installed and/or insulated window is like having a giant hole in your home’s exterior — and you will see the proof in your energy bills.

When it comes to window choice, there are several options, which can be overwhelming for some homeowners.

It used to be that all you could get were single-paned windows — those are windows that have just one sheet of glass. Now you can get windows that are double- or triple-paned, windows with argon or krypton gas, low-E coatings in between the panes — and different combinations of each, like low-E double-paned windows or low-E triple-paned windows with argon gas.

What’s the difference? For starters, a double-paned window has two layers of glass; triple-paned has three. Multiple layers of glass allow for insulation to go in between the panes, and that boosts the R-value.

The most common types of insulation are argon or krypton gas. Both help stop heat transfer. Krypton insulates better than argon but it’s also more expensive. If you have the budget, it’s a good investment. However, argon-gas-filled windows are still very good; if a home has these windows, I wouldn’t be disappointed.

If you’re not the original owner of your home, you might not know if your windows are gas filled. When you bought the house the previous owners would have probably told you, since they do make for better windows and cost more.

But if you want to make sure you can check the window tag. It’s usually on the bottom inside track of the window.

You can also try looking for two small holes on the spacer — one hole is where the gas would have been injected, and the other hole is for air to exit.

Another feature to look for is low-E glass, or low-emissivity glass. This is a microscopic metallic-oxide coating on the glass that lets in light but also helps stop heat — and ultraviolet rays — from transferring through the window.

Sometimes heat transfer is a good thing. In the winter, we want the sun to help heat our homes. But I’ve heard some homeowners complain about turning up their furnace more often after installing triple-paned windows. That’s because some windows do an excellent job at stopping heat transfer.

However, just like they help stop heat from escaping your home, they also don’t let the natural heat from the sun come in.

One option is to have triple-paned windows on the north side of the house only, and then double-paned on the rest. This provides the extra insulation needed to help block north winds, but still allows some heat to get in on all the other sides. It’s a tricky balance, which is why you should talk to a pro.

Once you’ve decided on the type of glass you want, you have to choose the framing. The most common are wood, metal — and vinyl, which tends to last longer and is easier to clean.

Metal can get scratched and dented. Wood is nice but requires a lot of maintenance; you will need to repaint your window framing at least every five years, and that’s if it’s done really well. The natural expansion and contraction of the wood frame can crack the paint. The basic rule of thumb is that if you can see the wood, the frame needs to be re-caulked and re-painted.

What type of window is the best? Most people want an easy answer. But like most things, there is no easy answer. It depends on the house and the application.

The key to making the right choice is finding a professional who will know what type of windows will work best for your home, and who will make sure they are properly installed.