Insulation Or Generation: Two Ways To Turn Old Houses Into Zero Emissions Homes
Fantastic progress is being made on lifting energy efficiency standards for new homes around the world, and the concept of building new homes to a ‘net zero energy’ standard is becoming mainstream. That’s great, but a typical house stands for decades, and a lot of older homes are not much better than tents when it comes to heating and cooling them.
So how can the energy performance of older homes be improved? Or to be even bolder, how can they be converted into net zero energy homes in a cost-effective way?
I’ve come across a couple of programs recently that take quite different approaches to achieving this aim.
Clearly, the better the insulation and thermal properties of a dwelling, the less energy needed to heat or cool it. This is the approach being taken in The Netherlands where older homes are being converted to net zero energy at zero upfront cost, no subsidies and with a 30 year builders’ guarantee. While solar panels on the roof are one component of going zero net energy, much of the attention is on insulation, glazing and ventilation.
So how does the substantial cost of over 40,000 Euros (A$58,000) for each retrofit get covered? It basically comes down to converting former energy payments into loan repayments.
But there’s a catch. In The Netherlands, a lot of housing is owned by social housing associations. There is also a lot of standardisation of the actual home units. This allows retrofitting to be conducted as an industrial process, benefiting from the economies of scale of being able to develop standardised retrofitting packages. The combination of housing associations and similarities in housing stock allow for bulk roll-outs of the program. As its proponents admit, that means it is only viable in a limited number of countries.
Change the power supply
The United States is one country where the diversity of housing stock and individual ownership would rule out the Dutch model. So in a low-income neighbourhood of outdated housing stock in Houston, Texas, an initiative is underway to create a micro-grid powered largely by renewable energy.
This project is in its infancy and involves a lot of different stakeholders, so its future is far from certain. It also isn’t clear to what extent the project is focusing just on renewable energy generation as opposed to upgrading the building stock. There are likely to be some relatively low cost, quick payback improvements that could be made to the fabric of homes. The question then would be whether, in a low income community, suitable financing packages for retrofits can be offered.
Mix and match
The best approach to creating zero emissions housing will depend to a large degree on each situation. With the declining costs of wind and solar power, there may well be situations where it is cheaper to generate than insulate. Local climate will be a big factor – Houston and Amsterdam are poles apart in this regard.
But financial cost may hide a more important calculation. What is the lifetime energy use, including the embodied energy of any retrofits, in each case? In an ideal world, the lowest overall lifetime energy consumption wins.
Title image: Knauf Insulation & Intel Free Press via Flickr (CC)