Use Your Roof As a Solar Space Heater
Use your existing roof and insulation membrane to supply solar heated air to your home. Whenever the roof is heated by the sun the air trapped underneath is naturally heated ,it then rises to the highest point where you can collect it to heat your home. Most metal roofs and some other types of clad roofs have an insulating membrane underneath them,it becomes a very simple, inexpensive, project to automatically harvest this warm air to heat your home at almost zero cost.
Steps
- Access the roof space of your house and make sure that your roof has an insulation membrane under the roofing sheets.
- Locate the top two purlins either side of the roof ridge
- Now tidy up any excess insulation. Use a hand tacker staple gun to neatly secure the insulation to the purlins along the whole length of the ridge.
- When finished each side of the roof should now have insulation running from the gutter to the height of the top purlin.The space between the purlin should be open to the underside of the metal forming the ridge.
- Cut strips of insulation wide enough to fix across the underside of the top two purlins and long enough to run the length of the ridge.
- Fix this insulation to the underside of the top two purlins with your hand tacker, thus forming a header between them. The air between the roof sheeting and the insulation will be heated by the radiation of the sun.It will rise toward this header and collect there.
- Near the center of the ridge fit a suitably sized duct outlet.( if you intend to use a six inch ducted fan then you should use a matching 6 inch duct) Fix it to the underside of the purlins. Seal to the foil using silicone or similar product , making sure that the portion of foil directly under outlet is removed to allow the heated air to flow from the duct.
- Fit a ceiling duct outlet to the ceiling of the area you wish to heat.
- Fit a suitably sized ducted fan somewhere between the duct from the ridge and the duct to the ceiling.Best practice would entail suspending the fan from the roof structure using a heavy duty spring . This will prevent vibration from the fan if it becomes out of balance due to dust building up on its blades)and will insure quiet operation.
- Measure cut and fit two lengths of foil ducting.One to connect your ridge duct to the fan and one to connect the fan to the ceiling duct.
- Fit a thermostatic switch near the duct at the header and position the sensor bulb inside the header near the duct opening. Secure the bulb to the purlin.
- Wire the fan to the thermostatic switch so that the fan will only run when the temperature of the air in the header, exceeds the control temperature of the area to be heated.
- Move to the outside of the roof and seal any air gaps between the ridge of the roof and the roof sheeting profile.( you could use expanding foam or a proprietary profile seal.)
- Your heater is ready to use at this stage and it will contribute many hours of free heat during days where the sun shines despite the air temp being cold.
- To really get most benefit the top meter or so of the ridge should be covered with a clear plastic cover. this how to will be amended to include this option.
Tips
- A building incorporating this simple inexpensive and reliable system will provide opportunistic heating, cooling, and ventilation throughout the year and every future year ; turning itself on /off automatically for the cost of running a 60 watt fan .
- This system can be upgraded at any future time by providing part or all of the upper roof surface with a transparent cover of any description, but even without a cover there is significant heat to be gained at no cost.
Warnings
- Be aware that your roof/attic needs ventilation to get rid of excess heat and humidity in summer and winter. Blocking or trapping this heat and moisture in the roof structure can lead to early failure of shingles and roof deck wood. Possibilities of mold and mildew blooms.
- You will need an electrician to connect your fan and thermostat unless you can access a low voltage ducted fan
Things You'll Need
- Some foil insulation
- Six inch ducted fan
- Foil ducting
- A hand tacker
- Thermostatic switch
- A thermostatic switch to control at room temperature
- length of roof profile seal
