Our house, like many old houses in this part of Australia was not designed well for the local climate. In an area that is quite cool, the house was built with minimal windows facing the northern sun. Australian’s have a love affair with verandas and generally that’s ok because most of them live where it is usually hot. What is needed here is passive solar design.
We found we did not use the veranda often because it was either too hot, too cold, too windy, too many flies buzzing about, too many vicious mosquitoes or there was just too many other things to do. It was just a waste of space that required regular maintenance. We decided to convert it into a sunroom and become lovers of the sun.
I won’t go into too much detail about the build as I’m not a builder and this post is really about the benefits of passive solar design.
The build started with help from my father to replace the floor. Then I ordered a lot of windows and a glass door.
A massive hail storm hit the town before our windows were built. Many windows around town were smashed and repairing those was the top priority for glaziers so our windows were delayed until around the time our first baby was born. This added some extra pressure at a time when we didn’t really need it.
Once the windows and doors were in place I removed an existing window between the kitchen and the new sunroom and converted it into a doorway. Next job was fastening some plasterboard over the old weatherboards and hiring a plasterer to finish it off. We got an electrician to install lights and a power point and then we painted the walls and bought and carpet and had that installed. On the exterior we had to add a row of brickwork around below the windows and a small section of tiling at the front door.
All up it cost around $10 000. That was 15 years ago, so these prices are out of date. The windows and glass front door were the biggest cost at $7000. We needed 100 meters of fabric for the curtains and our family helped by sewing these. Even so, with curtain rods the total for that was around $1000. The final $2000 went on flooring, carpet, electrician, plasterer and paint.
How good is it?
Aesthetically it is ok. You won’t read about it in Home Beautiful. It’s not going to win any design awards. From a practical viewpoint it’s great. A lot of projects that I have done have not been successful, but this was more successful than I imagined it would be. It went from the least used area of the house to one of the most used. Visitors gravitate to it and are usually surprised at how warm it is inside.
Some people are surprised that a sunroom will significantly warm a house although they are not surprised at how hot the interior of a car can get parked in the sun and there really is not that much difference between the two. There is roughly 1KW energy per square metre from the sun, or so I beleive. About 14 square metres of sunshine enters through the front windows at midday in winter, so I think that we are getting about 14KW of energy. It doesn’t all get retained as heat as some is reflected back out, but it’s still substantial.
We have a wood heater that is very good, but it only outputs around 10KW of heat. We have a reverse cycle air conditioner as well and it is ok, but it only outputs around 6KW of heat. The sunroom makes a far bigger contribution to our heating than either of these. It only takes a cloudy day to be reminded of this, although even when it is cloudy there is often some warmth in the sunroom. It is now our main heating source with the wood heater only required on cold nights and the reverse cycle usually only on cool mornings when the wood heater has not been used overnight.
During the day it is often 10 – 15°C warmer inside the sunroom than it is outside. It’s not uncommon for it to get up to 28°C (82°F) inside when it is only 13°C (55°F) outside. We usually wear tee shirts in winter and still feel very warm. Parts of the house further away from the sunroom are not as hot as that, but generally they reach very pleasant temperatures.
It has changed our house from a cold old house into a warm, light and pleasant place. If you live in a cool climate and you get the opportunity to visit a house that uses passive solar heating then see what it’s like. Using “alternative” technology does not have to be inferior – it can be superior.
When you have as many single glazed regular glass windows as we do it doesn’t seem to matter if curtains have thermal backing or not, or even if you draw them closed or not, it is still going to get cold overnight. Maybe the temperature will not drop quite as quick but it seems to be just as cold by morning. We overcame this by shutting the sunroom off from the rest of the house at night.
Windows on the northern side (in the southern hemisphere) are good. The sun shines in during winter, but not in summer. Windows on the west or possibly the east are not as good. We place a temporary awning above the western windows during summer to reduce the sunshine entering the house otherwise the house would be unbearably hot.
A concrete floor with a high thermal mass should absorb and store heat during the day and release it during the night. That was too difficult for me to do, so we don’t get that benefit.
The sun is harsh on carpet, paint and furniture. We currently have three chairs. We deliberately use old ones. Only one was purchased new, one is second hand and the other came from our local dump shop. Covering them will lengthen their life, otherwise they will not last many years.
Cleaning the house windows became a big job.
To work well the room needs to receive plenty of sunshine. A cloudy climate of shading from trees and buildings will make a vast difference.
This is the second post about solar projects we have tried. I have already covered using waste heat from the roof to warm our house. Still to come is our experience with solar hot water heating and grid connect solar electricity systems.