Let warmth into your home

The other day we were driving home at about 5.30pm, just after sunset, and could barely make out plumes of wood smoke exiting cowls on Heads Road and Cornfoot Street.

The day had been sunny, but cool, as would be expected in July. Our curtains were still open, but upon entering our old villa on Arawa Place, we were pleased to feel the warmth gifted us by the sun. The thermometer in the kitchen read 23C.

Unfortunately, Whanganui has been left with a legacy of thousands of homes built with seemingly no regard to the sun or even thermal comfort for that matter. Many of the dwellings I've audited during the past three months through Project HEAT share these characteristics: cold in winter and hot in summer.

Our home would have been the same before its passive solar renovation. The "solar collectors" we used already exist in every home in the country: windows. The problem with most homes is that the windows are evenly distributed between the north, south, east and west.

On sunny winter days, only the northerly-facing windows have a positive energy balance. In other words, they gain more heat through sunlight energy during the day than they lose through radiation at night (if properly curtained, as you would). All of the other windows have negative energy balances even on the sunniest of winter days.

For us, the obvious solution was to shift windows from southern exposure to northern. While retaining roughly the same amount of total glazing, we were able to dramatically improve the solar gain of this old villa where, once upon a time, someone decided to put the toilet in the north corner. Shifting it to a more appropriate location was accompanied by opening up the north corner to create a bright, cosy kitchen with French door access to backyard vege gardens and an outdoor pizza oven.

All of the work was done in accordance with the New Zealand Building Code, with special attention paid to weather-tightness and bracing.

At the same time, we insulated the ceilings as well as those walls that were opened up during the renovation. And finally, we added thermal mass inside of the building envelope to moderate and store solar thermal energy, but that, my friends, is a story for another day.

Only four days left for Project HEAT - free, practical energy-saving advice. Ring me on 06 344 5013 or 022 635 0868; please no texts.Ask a Solar Question, September 5, 7pm to 9pm at the Quaker Meeting House, 256 Wicksteed St. Registration essential - phone Ces on 06 345 4717.