Problem 2: The thermal envelope

The house had the bare minimum of ceiling insulation.

Doubling or even tripling the layer of insulation in the ceiling is one of the best and easiest things you can do to improve a dwelling's thermal envelope. The Building Code minimum specifies the very lowest level of insulation, so if you're building a new house, you need to go well above it.

The solution Insulation

I removed a couple of sheets of roofing iron to make it easy to install the large rolls of blanket insulation.

I over-ordered and used the excess to cover the ducting of the existing heat transfer system. This unplanned, simple retrofit turned out to be one of the best of the entire project (see page 20).

For the walls, I chose the ones that could be most easily insulated without penetrating the internal or external linings (which in most cases would require building consent).

On the four walls I've done so far, I've attached evenly spaced 50-70mm framing timber to the inside face of the wall, then insulated the gaps with polyester batts. It includes this feature wall in the master bedroom (right), a plywood climbing wall in the kid's room, a wall in the office, and two closets along a south wall.

Glazing

At present nearly all the French doors (we have four sets) and windows have either double glazing or perspex secondary glazing.

The choice of which one to use goes right to the heart of my eco-thrifty approach, based on observations I've made over the last decade.

If you have timber-framed windows and apply secondary glazing on the inside, moisture may still get between the panes on the windward side of a home during heavy rain. It can take days, sometimes weeks, to dry out unless the panel is removed (screws or magnetic).

That's why I only use secondary glazing on timber-framed windows where winddriven rain won't reach the putty, such as in recessed entryways, on covered decks or carports.

Otherwise, I consider the best choice is to retrofit double-glazing with low-e glass.

The window from our dining nook looks out to the carport. Since the outside isn't exposed to rain or direct sunlight that could degrade the panel, I ‘triple glazed' it with layers of Perspex applied internally and externally.

I also converted a traditional four-panel glass door into an insulated one on a budget of next to nothing by reusing second-hand materials and small offcuts (see page 19).

We now also have lined Roman blinds for the kitchen and dining areas and detachable curtain linings for the existing unlined curtains.