The mantra of low energy architecture is fabric first, translated as: spend your capital on insulation, good windows and airtightness before you investigate heating and renewable energy. This may be easier to apply with new construction, but is more difficult to apply when renovating. Listening in to conversations at stands exhibiting insulation products for renovating was akin to hearing an insurance salesperson list policy exclusions; building consent required in some situations, underfloor insulation not always achievable, flat roofs can be problematic. In contrast, heat pumps and other bolt on accessories for energy efficiency sail above all these issues.
So why, despite these difficulties, is a fabric first approach so important when looking to improve our existing housing stock?
If we take a 4kW heat pump in a 150sqm house in Wellington or Christchurch as an example.
- In an uninsulated house this much heating output will struggle to heat one room to 20 degrees in winter.
- In an average new home, this much heating output will heat an open plan living area to 20 degrees in winter.
- In a low energy house, 4kW will heat the whole house to 20 degrees in winter.
- In a PassivHaus, 4kw is too powerful; 1.5kW is sufficient to heat the whole house to 20 degrees in winter.
Most of the housing that is here today will still be here in 30 years. If you are approaching the issue from a government point of view, encouraging fabric improvements are easy pickings. The way to access this opportunity is to change the regulatory and economic environment so that conditions are more favourable for home owners and landlords to invest in these measures. Other countries such as Germany and the UK have come to this conclusion and have instigated the necessary changes to positive effect (This topic will be covered in a later blog post). So in the meantime, if you are struggling to keep your home warm, seek out, take advantage of and support centralized measures for improving energy efficiency in housing. And make sure you've done all you can to insulate and draft proof your house before shopping for a heat pump.