Making an Energy-Efficient Solarium

bright sunroom - making an energy-efficient solarium

A solarium is a beautiful addition to a home: bright, airy, cheerful and often brimming with greenery. It’s not, however, the most energy-efficient of rooms.

On the surface, it might seem like a solarium should be efficient, at least in winter, what with all those sunbeams pouring in. And in fact, some manufacturers will claim that solariums can help passively heat your home in the colder months.

Camille Ouellette of Ecohome warns, however, that the common perception that solariums will lower your heating bills in the winter only applies to “moderate climates such as in Europe or even in the milder regions of the United States.” For those of us living in colder climes, a conventional solarium will drain heat.

That’s because an under- or uninsulated structure can’t keep warm air inside. The sun’s rays can get in, but the heat they generate is always being pulled back out through the walls and roof. Not such a problem when the sun is shining directly into the room, supplying constant new heat, but once the sun goes down, the solarium becomes a serious energy drain.

So how to maximize energy efficiency in a solarium? These strategies might help. We’ll start with some suggestions for people who already have a solarium and want to make what they have more efficient, and then offer considerations for those who are building from scratch.

Retrofitting a Solarium

Even if your solarium set up is not ideal, there are some measures you can take to moderate temperatures and make your space more comfortable, more of the time.

Caulk the Frames

Air leakage is a big source of heat loss in a sunroom. Caulking needs to be regularly inspected because solarium windows are subject to more moisture than regular windows are. Condensation will be a natural by-product of warmed air meeting the cooler glass, especially in winter. Fluctuating temperatures also put extra strain on caulking, so make sure yours is in good repair to avoid leaking conditioned air.

Add a Window Coating

Replacing all the older windows in a sunroom might not be financially feasible, but a lower-cost option is to coat them. Low-e (low-emissivity) films can be applied to existing windows to limit UV rays as well as heat transfer. Tinting can also help moderate the amount of light and heat that gets into the solarium. The downside with tinting is that it’s a permanent solution and you can’t adjust it with the seasons.

Install Window Coverings

This might defeat the purpose of the solarium for you, but hanging blinds or insulating curtains is a low-cost, versatile way to moderate light infiltration. You can open and close them at will and while you’ll certainly lose your view when you close them, you’ll also be mitigating heat transfer.

Install Retractable Awnings

Retractable awnings are a more expensive solution to heat issues, but they will allow you some versatility in terms of when to allow light and heat into your sunroom. They might also be a useful solution for homes that don’t have trees to provide cover.

Building a New Solarium

sunroom - making an energy-efficient solarium

When you build your solarium from scratch, you’ll have the advantage of incorporating energy-efficiency measures right from the start. Here are just a few things to consider.


You might be limited as to where you can add on to your home, but if you’re lucky enough to have a few options, consider using your property to help passively control the temperature of your solarium.

Solar south is usually the target orientation, but the south-west or south-east sides of your home could be a better spot in terms of creating ideal temperatures. Your sunroom will get more of the morning or afternoon sun, but it won’t cook in the midday heat when the sun swings around. This all depends, however, on the specifics of your site, including elevation and surrounding features.

Leverage deciduous trees on your property to help shade the solarium in the summer and let the sun through in the winter, when you’ll need it more. If you have no existing trees that can do that job, consider planting some.


Lean-to styles with sloped glazing will get hotter, says the Department of Energy. They recommend vertical glazing to maximize heat gain in winter when the sun is low and minimize heat gain in the summer, when the sun is higher in the sky.

In addition, they suggest that “vertical glazing is also less expensive, easier to install and insulate, and not as prone to leaking, fogging, breaking, and other glazing failures.” They also recommend insulated side walls, as opposed to wrap-around glass.

In terms of the roof, consider that glazed roofs are prone to damage. While it’s lovely to have that clear view of the sky, an insulated roof will also be easier on your bills.

Floors with a higher thermal mass (like stone) will be better at absorbing heat, especially if it’s a darker colour. That means they’ll store heat during the day and release it more slowly in the evenings. Ouellette suggests that interiors should “include materials with high thermal mass and dark color in the direct path of the sun to absorb heat and balance temperatures.”


One of the most important aspects of an energy-efficient solarium, of course, are the windows. This is not the place to skimp—investing in high-quality windows here could save you many headaches down the road.

Triple-pane windows are the gold standard. Look for windows with a low U-Factor—the lower, the better. U-Factor measures how much heat will be transferred through the glass when indoor and outdoor temperatures differ. A low U-Factor means a better-insulated window.

Check window stickers for the solar heat gain coefficient (SHGC), as well. This number measures how much heat the glass itself will absorb and release into your indoor space. Folks in warmer climates might want to opt for a low SHGC to minimize additional heat. Homes in colder climates might want a higher SHGC to increase heat gain.


Good airflow is essential to an efficient solarium. Plan on ceiling fans to help circulate the warmed air, as well as operable windows to create a breeze. Ventilation fans near the ceiling can be used to exhaust hot air back outside, or circulate it into the home, depending on season.


Despite the extra attention and labour that a solarium requires, the trade-off might be worth it to have a little extra light, warmth and space in your home. And the more efficient your solarium is, the fewer issues you’ll have down the road.

Feature image: Francesca Tosolini; Image 1: KCDM

Written By
More from Mary Read
Tired of Paint? Try These Sustainable Wall Covering Options Instead
Paint is fine. You know. Fine. It’s everywhere, because it’s inexpensive and...
Read More
Leave a comment

Your email address will not be published.