Cooling your Sunroom

Do not underestimate how hot your conservatory or sunroom can get during the summer months. If you live in a country where in the summer the temperature regularly gets above about 20C then you have to thinks seriously about cooling the room. There are various approaches to keeping the room nice and cool, some more expensive than others.

Air-vents

Its most practical to consider air vents during the design phase of the sunroom. On a hot summer day a sunroom feels like a sealed box (which it is). The hot air in the room will rise to the ceiling. Placing good ventilation near the top of the sunroom can allow some of this hot air to escape thus preventing the heat build up. Care must be taken to ensure that the design of the vents means they are convenient to open for you, weather proof and inconvenient for a burglar to get into!

Good natural ventilation can be unobtrusive and reasonably effective at reducing the air temperature, but on a really hot day it is unlikely to be enough to keep the room cool enough to use.

Sunroom Blinds

Blinds serve three purposes

  1. Dress the room making it seem less like a glasshouse.
  2. Make the sunroom more homely if used in the evenings, the light reflects of the blinds instead of having the blackness of outside and reflections.
  3. Reduce the temperature rise due to external sunlight.

It is the latter that is of interest. Blinds reduce the amount of direct sunlight that is incident on you in the sunroom. They can come with a reflective coating on the outward facing side that will reflect most of the light. However, this action is done after the sunlight has reached the inside of the room. What can happen is the heat can get trapped between the blind and the window, but will ultimately escape and raise the temperature of the entire sunroom or conservatory. My personal experience, with my south facing sunroom, is that whilst blinds reduce the temperature inside the room they are not alone sufficient on a hot day.

Fans

Fans work by increasing the rate of heat removal from your body. They do this by blowing air across your skin and on a hot day cool you effectively through evaporation. Fans can either by mounted on the ceiling of your sunroom or as a pedestal or free-standing fan. Ceiling fans do increase the air flow around the room but tend to blow down the hotter air that accumulates in the roof space. Free-standing fans can feel more effective as the are typically mounted nearer to the person in the room. Again, these help reduce the apparent air temperature in the room but aren't alone sufficient on a hot day. 

Solar Coatings

Unlike blinds, solar coatings are placed on the windows that make up the majority of the surface of your sunroom. The typically act to block certain wavelengths of 'non-visible' light from entering the room. This means they can reduce the amount of energy being delivered by the sunlight without having much effect on the amount of visible light entering the room. I've never tested these coatings personally. They could be more effective as they have a chance blocking the 'heat' from entering the room. I know of someone who spent about $10,000 on roof glazing with a solar coating and the room still needed to be air conditioned. This technology is improving all the time though and the processing and coating on the glass is getting better at stopping heat input. Certainly one to consider but ask for a demonstration if possible.

Evaporative Coolers

Evaporative coolers work by forcing air over a wet surface. As the water evaporates from the surface it cools the air which in turn is expelled into the room. This efficiency of this method can be improved by placing ice in the cooling compartment. It is not as effective as air conditioning, but typically much lower cost. The units are typically portable and are more effective at cooling than fans alone.

Air Conditioning

Air conditioning units will cool your sunroom. The question is how much are you willing to pay and how noisy a unit can you tolerate? Air conditioners are 'phase change - liquid to gas' coolers like evaporative coolers except for two things. One the heat transfer rate (or how much heat they can remove out of the atmosphere) is much greater and secondly they typically expel this hot air outside the sunroom via an exhaust vent or pipe.

Portable air conditioners units are popular in Northern Europe where air conditioning is less common. Typically they are more expensive, noisier and less powerful than split air conditioning units but have the convenience of being used in other rooms and are essentially usable 'out of the box'.

Fixed position air conditioning is the one to consider if you are having a new sunroom built. The compressor or engine of the system can be positioned outside the sunroom, reducing both the noise and amount of hardware visible in your sunroom. The amount of cooling power is really up to you and what you think you conservatory will require for cooling. This is why there is no reason why an air conditioning unit could not cool your room given no other constraints.

A factor to consider with these units is noise. The portable units are noisy (50-70 dBA) with the split units running at 40-50 dBA typically. For comparison 30-40 dBA is the noise level in a typical quiet living room. 10 dBA represents a doubling of perceived noise level.

Sunroom Cooling Summary

None of the methods, apart from air conditioning, is enough alone to cool your sunroom on a hot summers day. My experience suggests that you need air conditioning, preferably a suitably powerful split unit. Combining this with a solar coating or blinds will reduce the energy consumption of the air conditioning unit and maybe allow it to be used a lower, quieter setting.

Blinds or solar coatings? Whilst solar coatings have the advantage of position on the outside of the sunroom, blinds can be used as a decorative feature and which, if any, you choose is personal preference.

As a final note just think carefully in the sunroom design what the room will be used for, when it will be used and how hot it is likely to get during the summer months and plan your temperature regulation properly.