Passive solar home design

ARTICLE Jason Burgess

Designing for the sun is nothing new. When the Greeks laid out the City of Priene on the slopes of Mount Samsun, 2,400 years ago, it was planned so that the porticos in every home caught the warming winter sunlight.

photonewzealand/Damonte; Bruce/Arcaid/Corbis
Using the ancient wisdom of the Greeks in your renovation will not only create an energy-efficient home, it will save you hundreds of dollars on your future power bills. Simply put, passive solar design should be paramount when planning a new home or renovating an existing house.
“It doesn’t have to be an expensive exercise,” says Ella Te Huia, Energy Efficiency Consultant at Smart Energy Homes. “A lot comes down to making some common sense decisions. And at the end of the day, it all adds value to your home.”
The object of passive solar design is to allow as much direct sunshine inside the home in winter, to heat an insulated ‘thermal sink’ such as a concrete slab floor and sometimes, walls. That thermal store of warmth is then slowly released back into the home as the day cools.
“Energy is built into the structure,” says Albrecht Stoecklein, Technical Manager at Right House. “When it comes time to renovate, that is the time to upgrade the building envelope effectively and affordably. Don’t be distracted by door handles and design features, those things can be fixed cheaply later.”

Maximising solar gain comes down to the position of your dwelling, having sun-facing windows (double glazed); creating insulated thermal mass within the home; shading; ventilation and above all installing the highest R-value wall, ceiling and floor insulation.
“The key to energy efficiency in any home is insulation,” says Albrecht. “Everything else is secondary, because energy prices will keep going up.”
Effective passive solar design can reduce the cost of heating and cooling by as much as 30 per cent. In a super-insulated house, passive solar will achieve even more than that.
While Ella recommends using skilled installers to fit the insulation, she urges DIY to handle some of the small things themselves, like fitting thermal-lined drapes and draught stops to doors and windows.
“Twenty-five per cent of heat loss is through draughts. At the window area make sure the curtains are at least 100-200 mm longer than the sill and install pelmet covers to trap warm air in winter.”

photonewzealand/Damonte;Bruce/Arcaid/Corbis
The orientation of your property and home affects how much sun you receive and will impact on the comfort and energy efficiency of your home.
“Does the orientation of your house design support passive solar? That’s the first question you should ask,” says, the Refresh Renovations Builder.
In an ideal world, the long axis of your home should lie in the east-west direction, with the living spaces facing north. This orientation can be plus or minus 20 degrees of north without having a major impact on efficiency. Other factors like trees, ridgelines and buildings may also shade your home in winter months.
Living in a house for at least a year before you renovate is possibly the best way to assess where the sun falls during each season. Whether you have that time or not, engaging an energy efficiency consultant will save you money in the long run.

Five elements of passive solar design - US. Department of Energy
Using sun calculators, modeling tools and thermal imaging cameras, they can short cut the process and provide cost effective solutions for the trickiest of locations.
South and east-facing sloping sites may have limited direct solar access. “In a situation like this,” says Ella, “skylights and a step roofline with windows on the north side will allow the sun in. An internal, heat-absorbing Trombe thermal wall in conjunction with appropriately positioned double glazing may also be an option.”
The north side might also benefit from a conservatory, again this needs to be carefully considered and constructed in tandem with a purpose-designed thermal sink like a masonry-tile floor to collect the heat.

Glass is a great conductor of heat, and north-facing windows will provide the best access for solar gain. In winter single glazing can lose up to 50 per cent of heat, even in a fully insulated house. If possible, avoid south facing windows or replace existing ones with double glazed.
Even if the builder does not specify using double glazing, it is a key component to the energy efficiency of the building envelope. Like insulation, the higher the spec of the product, the better the result.
Double glazing traps a layer of air between two panes. Air is a very poor conductor of heat, so the trapped layer sets up a blanket of protection between cold air on one side and warm on the other.
Look for energy efficient Low-e or low emissivity glass. This glass has a special metal insulating coating that increases the energy efficiency of windows by reducing the transfer of heat or cold through glass. For maximum effect in colder climates, argon filled and triple glazing with Low-E glass will be the most beneficial.

You might be interested in reading: Consider solar for your home.

 

This article by Jason Burgess featured on page 82 of Issue 012 of Renovate Magazine. Renovate Magazine is an easy to use resource providing fresh inspiration and motivation at every turn of the page.

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*All information is believed to be true at time of publishing and is subject to change.