Walls or windows?
All homes should enjoy the benefits of insulated walls AND double glazing but installing wall insulation should be considered first. Here’s why.
For every $100 spent on heating that escapes through windows and walls:
Uninsulated walls lose $64, which reduces to a mere $9 when insulated with Insulmax®...
Timber framed single glazed windows lose $36, which reduces to $27 when replaced with aluminium framed double glazed units.
Let us explain…
Heat is able to move across all types of material and structures at different speeds and the larger the surface area the more heat is lost.
A typical 100 square metre home has about 81 square metres of exterior wall and about 27 square metres of windows and doors - so about three times more external wall area than windows.
While an area of glass loses ≅50% more heat than the same area of uninsulated wall (all things being equal), when you consider that your home has about 3x more wall area than window area, the total heat loss from walls is significantly more than from windows.
We pay for heating and most of that heat escapes from uninsulated parts of our home. If your home has ceiling and underfloor insulation, the uninsulated walls and glazing are losing the largest amount of heat.
Consider a typical weatherboard home. For every $100 spent on heating that escapes through walls and windows, approximately $36 is lost through timber framed single glazed windows, compared to approximately $64 lost through uninsulated walls.
When you Insulmax® your walls, you're adding at least 100mm depth of high performing thermal insulation to the wall structure. This dramatically reduces heat loss - by approximately 86% - making a substantial improvement to a large surface area of your home.
However in the real world, insulating walls with Insulmax® dramatically reduces heat loss by approximately 86% making a large improvement to a relatively large surface area of your home. This is because at least 100mm of high performing thermal insulation can be added to the wall structure.
Compare this with the typical option of replacing single glazed timber framed windows with double glazed aluminium framed windows. This adds about 6-10mm of air and 4mm of glass. This change results in about a 25% reduction of heat loss
The benefit of insulating walls with Insulmax® is far greater than replacing windows with double glazed units. Low E, argon, uPVC or timber frames all increase the efficiency of double glazing but give relatively marginal improvement because the basic process of double glazing can only add about 4mm of glass and 6-10 mm of air.
The cost of insulating exterior walls with Insulmax® is far less than the cost of double glazing your home and has a greater benefit. The cost benefit of double glazing is recognised in NZ Building Standards as wall insulation became mandatory in new builds from 1978 compared to double glazing which became mandatory in new builds 20 years later in 2008.
Every building material or structure has an R value which is a measure of how well the material or structure allows heat to flow through it. A woolly jumper would have a high R value and an aluminium saucepan would have a very low R value. Roughly speaking if the R value can be doubled the amount of heat flowing and being lost will be reduced by half.
Insulation ratings are derived from Design Navigator, a leading New Zealand industry resource in the calculation of building variables. Insulation ratings of windows are sourced from The New Zealand Window Energy Efficiency Rating System
Framing assumed to be 100mm x 50mm framing and 450mm centres with nogs at 800mm centres and exterior rusticated weatherboard. Interior 10mm plasterboard insulated with the addition of R2.8 Insulmax®.
Whole wall structure uninsulated R0.32
Whole wall structure when insulated R2.3
Heat flow/loss reduction approximately 86%*
Timber frame single glazed window R0.19
Aluminium frame double glazed window R0.26
Heat flow/ loss reduction approximately 25%*
Note: the insulation rating of double glazed windows is lower than the insulation rating of an uninsulated wall structure meaning that once double glazed, windows are still losing more heat than the same area of uninsulated wall