Free heat from the sun

Published Tuesday, May 26, 2015 in the New Brunswick Telegraph Journal and the Fredericton Daily Gleaner.

Passive solar heating – capturing and enjoying free warmth from the sun – probably dates back to when our forefathers discovered that south-facing caves tended to be a lot warmer than any others.

They were onto something: today, we know that homes and other buildings can get significant amounts of their heat from the sun, for free, without solar panels or any special technology.  Here are a few tips for maximizing that free heat from the sun.

New construction

If you’re planning to build, you have the perfect opportunity to take advantage of free solar heat.  For best results, follow a few basic principles:

1. Site selection: in deciding where to build on your lot, first determine where true south is.  (In NB, it’s 14 degrees east of magnetic south.)  For best results, orient buildings within 30 degrees of true south.

If possible, choose a slight south or southeast slope to get best exposure to the winter sun.  Trees on the north and upwind sides of the lot are desirable as windbreaks; trees on the south side will reduce solar gain and are candidates for removal.  Consider the impacts of neighbouring buildings, present and possible future.  

Finally, respect local bylaws regarding setbacks, water, sewage and power.  For specifics, check with your local planning authority.  

2. Design: you can minimize the amount of heat your building needs by minimizing the amount of heat it loses.  So insulate well and airseal tightly.  

Consider triple glazed windows instead of the typical double glazed.  Specify a low heat loss coefficient (called the U value) and a high solar heat gain coefficient (SHGC); both are expressed as decimals between zero and one.  Place more windows in south-facing walls and none or few in north facing walls.

Well-designed overhangs will admit sunlight and warmth in winter but provide shade in summer.  Blinds and awnings can help too.

3. Heat storage: incorporate plenty of building materials like drywall, masonry, concrete and ceramic tiles, which can absorb a lot of heat by day and radiate it back by night.   Google ‘thermal mass’ to learn more. 

Even in our NB climate, it's possible to design and build homes that require very little winter heat beyond what they get for free from the sun.  It’s wise to consult an architect specializing in solar design.

Existing homes

You may not be able to pick up a home and turn it toward the sun, but there are several things that can be done to increase the solar gain of existing homes:

As with new homes, efficiency is critical – so airsealing and adding insulation is always a good starting point.

Remove screens in the fall, so more light can come through; it only takes a minute and it makes a remarkable difference.  Give windows a good cleaning at the same time.

See if there are ways to reduce the winter shade your windows receive.  Things like the neighbour’s garage can’t be controlled, but things like trees and shrubs can be.  Total removal might be a bit drastic; often, a good trim will make a big difference.

If you are planning any renovations, strive to increase the thermal mass of your home with materials like ceramic tiles, masonry and even a second layer of drywall.  A bonus: homes with high thermal mass tend to be more comfortable because the temperature fluctuates less.

Use darker colors on floors and walls that receive direct sunlight to help them absorb more heat.

Use small fans to help distribute heat from warm areas of a home to cooler areas.

Close blinds at night to reduce heat loss through windows.

For more information, consult Solar Nova Scotia’s Canadian Solar Home Design Manual – it’s an excellent resource.

In both new and existing buildings, free heat from the sun is there for the taking.  We just need to be receptive to it.