How to Improve the Energy Efficiency of Your Sunroom

Modern Sunroom

Are you thinking of building a sunroom and want to make sure it doesn’t send your energy bills through the roof? Maybe you already have a sunroom, but you don’t use it as much as you’d like, because it’s either too hot, too cold, or just too drafty?

Here are a few tips to help you retrofit an existing sunroom to save energy. We’ve also included suggestions that will help ensure your new sunroom is energy efficient if you’re starting from scratch.

Sunroom Retrofits to Save Energy

It’s not uncommon for a sunroom to be freezing cold in the winter and intolerably hot in the summer. But there’s an easy way to fix this! The type of glass in your window panes is one of the biggest factors to affect your sunroom’s temperature—and therefore, your comfort.

In older sunrooms especially, the glass may be too thin to effectively moderate temperatures inside. The frames around the glass may also leak, too. Plus, depending on the design of the structure, there may not be enough insulation to keep conditioned air inside, while the external air remains outside.

Short of replacing the glass, here’s what you can do to improve energy-efficiency in the space.

  • Seal up leaks in the frames. Use a clear caulk to add weatherstripping around the frames and prevent air from leaking.
  • Tint the windows. Tinting reduces the intensity of sunlight, minimizes glare, and helps block the sun’s ultraviolet rays, which can fade furniture. A variety of tints are available that will prevent excessive sunlight from coming into the room. Choose a “low-E” radiant blocker, which will prevent radiant solar energy from entering the room in the summer, and will also keep radiant energy from escaping in the winter.
  • Cover the windows. In winter, use an inexpensive weatherization kit available at most hardware stores to add a layer or two of plastic film over the windows. Install it before the cold weather hits, and remove it once spring arrives. The downside of this approach is that you use and throw away a lot of plastic. Another alternative is to hang insulating curtains or drapes over the windows. During cold months, keep them open during the day to enjoy sunlight, but close them in the evening to keep out cold air and still enjoy the space. You can also hang reflective shades to prevent excessive sunlight from entering your room in the summer.
  • Add a ceiling fan. A fan will help cool the room down in summer and, with the blades inverted in winter, help circulate warm air.

New Sunroom Construction to Maximize Energy Savings

If you’re building a new sunroom, here’s how to make it energy-efficient from the get-go. Site it in an area that’s shaded in the summer but will still allow sun in the winter. In addition to choosing the spot where you actually have room for the sunroom, you’ll want a location that gets some sun. The ideal location would be one that can easily be shaded in summer but also take full advantage of welcome solar rays in winter. Can you position the room to be shaded by existing trees? Or, is there room to plant a few deciduous trees once construction is complete?

ENERGY STAR-qualified windows are a perfect place to start. Can you pick a sunroom design that includes retractable external awnings to provide shade as needed in the summer?  Because sunrooms may be 50 percent or more glass, choosing panes that don’t conduct hot or cold air is essential. In fact, regular window glazing or even double-paned glass just won’t cut it. You’ll need to pick glass that is properly rated for its U-factor, as well as something referred to as “SHGC.”

The U-factor of the glass indicates its “solar heat loss coefficient,” or its ability to retain or lose heat. The lower the U-factor, the better. A window made of single-pane glass has a U-factor of 1.1, which means it loses a lot of heat. The glass you put in a sunroom should have a U-factor of less than 0.3. Some manufacturers also coat interior panes with plastic film, which provides additional energy efficiency.

“SHGC” refers to “solar heat gain coefficient,” or the amount of solar radiation that gets through the glass. The lower the SHGC, the less solar heat it transmits and the greater its shading ability, which is more desirable in a hot climate. Conversely, a product with a high SHGC rating will collect more solar heat during the winter, which may be more desirable in a cold climate.

Maximize Insulation

If you’re building from scratch, choose a design that is easy to insulate, such as one with an actual ceiling and roof rather than floor-to-ceiling glass panels. Work with an experienced contractor to determine the type, quality and level of insulation your design allows, given your climate. Insulate both the space above the ceiling and the space below the floor, as well as in between glass panes if the design allows.

Heating and Cooling

If you want to use your sunroom all year long, you may need to either connect the room to your home’s HVAC system, or install a heating unit or air conditioning system. Here’s a sampling of the kinds of heating and cooling options that are commonly found in sunrooms.

Once you tighten up your sunroom, make sure you enjoy it! Relax, read, entertain. You can also use this delightful space as a mini-greenhouse to start early seedlings for your garden, to cultivate plants that you can move to other parts of your home, or even to grow herbs and sprouts you can cook with.

Do you already have a sunroom? How do you keep it warm and cool? Are you thinking about building a sunroom? What considerations are most important to you? Please share with us in the comments below!

13 Responses

  1. Lillian Schaeffer

    These are some great tips, and I appreciate your advice to maximize the amount of insulation in your sunroom. My husband and I are going to be building one on the back of our house, and we want to make sure it’s energy efficient and a comfortable place to be. We’ll definitely try to figure out a design that can maximize insulation, and we’ll be sure to get insulated windows as well. Thanks for the great post!

  2. I’m glad the tips were so helpful. Please let us know how your project goes!

  3. Betty

    I still cannot decide on the type of flooring I need for my sunroom. I get cool weather and hot weather.
    I looked at laminate and vinyl but Homedepot said it is not good for sunrooms. It cannot take the extreme cold and heat. Homedepot suggests carpet. I don’t want carpet. the floor is not leveled, ceramic is too costly. What can be used?
    Out of ideas.

    • I redid my sunroom and I live in an area that goes from one extreme temperature to the next. Lowes told me that the luxury vinyl planks were perfect for a sunroom with temperature change. It has been over a year and I have not had any problems.

    • Lauren Pezzullo

      Hi Betty,

      This post should help answer your question. Good luck!

  4. Hmmmm… would wood work?

  5. bob

    we have a sunroom with about 80% carpet and the other 20% vinel by the back door going out to the yard. Looks good works good.

  6. Good to know. I usually don’t think of carpeting for a sun room but, why not?

  7. I have Yorkshire Terrier show dogs, and have to use my sunroom to keep them in good coat. I have to keep ambient temps at a 70 degrees year round and it has been quite a trial. My sunroom had a cathedral ceiling so I hired a carpenter to build a regular ceiling and packed it with rolled insulation. The windows had triple glazing but still felt cold in the winter so I bought that thick crystal clear plastic they sell by the yard in fabric stores for picnic tables, and cut it to fit over each window taping it in place. It peels right off in Springtime, and I just roll it up and store it to use again for next winter. The floor is slate tile, but I discovered there was no insulation under the floor, so I got under the crawl space and packed it with fiberglass insulation, and that made all the difference. I still have to use a small window AC during the real hot months, and I do supplement with a small heater in the winter, but all in all I have made it a comfortable area for me and my dogs.

    • Lauren Pezzullo

      Sounds like you did a fantastic job. Congrats on the improved comfort and energy efficiency of your sunroom!

  8. Good Evening Diane

    We recently had a four season sun room built at our home. It is all glass including a glass roof. We love our sun room but find the cost for heating in the winter is extremely high.

    On the internet we recently saw a Solar Infra Systems Portable Solar Air Heater — 20 watts which can heat areas up to 150 square feet, We were thinking of buying one of these heaters and was wondering what you would suggest and recommend. Are there better portable solar heaters available that you would recommend.

    I thank you in advance for your assistance and look forward to hearing from you.

    Joe Berlettano

  9. That’s very impressive. I was going to suggest you could also hang draperies to reduce air flow through the windows, especially at night.

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