The Value of a Well Insulated House

The value of insulation

The better insulated and air tight your home is the more comfort you get from each unit of heat.

In fact homes can even be so well insulated and air tight that they only need the sun, bodies, appliances and some heat recovery to stay comfortable.  These homes are called passive houses.

In this final post of our Beginner’s Guide to Heating Bills we’ll look at why good insulation is so valuable.  Having touched on the average heating bill, heating fuel use, heating cost comparisons, home heat loss and thermostat temperature settings it makes sense to finish with insulation.

You see if you have exceptionally good insulation you don’t need to worry about heating bills at all.

The Value of a Well Insulated House

In the image above we depict the heat gains and losses for a ‘leaky house’, a ‘modern house’ and a ‘passive house’.  While it is tempting to look at heat gains first, it is actually the losses that explain what is going on.

The leaky house has solid walls, poor loft insulation, an uninsulated floor, single glazed windows and lots of draughts.  Because of this it needs 300 kilowatt-hours of heating for each square meter of space per year (kWh/m2a) just to stay warm.

The modern house has insulation in the wall cavity and loft, an insulated floor, double glazing and some draught excluders. Because of its better insulation it needs just half the heating of the leaky house, 150 kWh/m2a, to maintain a similar internal temperature.

The passive house has superb insulation in all materials, triple glazed windows that face the equator to maximize solar gains, and is so air tight it uses a ventilation system to keep the air fresh.  It needs just 15 kWh/m2a of heating, some of which comes from heat recovery in the ventilation system.

What does this mean in simple terms?  The leaky home’s heating bill might be $1,500 a year, $750 for the modern and $100 for the passive house.

What Does this Mean for Your Home?

Although this looks simple on paper really good insulation is actually rocket science.  And annoyingly for most of us investing in good insulation makes most sense when a home is originally built.  Cost effective retrofits take real talent.

That said if you own your own home many types of insulation are a good investment.  The colder your climate and the higher your fuel costs the better the paybacks are.

As a general rule you want to investigate the cheapest ways to improve your building’s envelope first.  This will probably start with caulking and draughtproofing.  Loft or attic insulation might be next.  Wall cavity insulation if you have one.  Floor covering and curtains may be old school, but can be really worth it if you’re on a budget or renting.

For major expenses like upgrading windows and external wall insulation the payback can be glacial, so you should really do your research and also factor in value changes to your home.

I hope you enjoyed the Beginners Guide to Heating Bills!!  In the future we hope to add more of a practical ‘how to’ guide about cutting heating bills, but this is a decent starting point to understanding your heating bills.

30 Day Shrink Guide
  • dieseltaylor

    What an excellent site. I have been following Which Conversations and the information here is so so much better than the partial information provided by Which? . They seem to be quite eager to avoid discussing the world gas energy market in order to provide a rallying point for a particular agenda.

    I have thought that with 2 million homes retro-fitted with cavity insulation by installers who offered the cheapest service there now exists a large opening in the market for thermal cameras checking whether the work has been done at all, or satisfactorily.

    • Lindsay Wilson

      I’ve considered thermal imaging a couple of time but still seems that touch expensive, even just to rent one. There is a cool start up trying to make a cheap iPhone addition. I’m really hoping they manage it!

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  • Tim Small

    Just to be clear – A PassivHaus still needs heating (and possibly cooling), but that heating system should hopefully be quite cheap to install, and need little to run…

    One of the Big Ideas in the original PassivHaus design was to make the heating system cheap to install by having it heat (centrally at just one point) the fresh air (which has already been warmed by the heat-recovery-system) used by the ventilation system. It doesn’t always work that well in practice tho’ for a number of reasons e.g. apart from anything else, the hot air doesn’t go directly into all rooms, only into bedrooms and living rooms. The Kitchen and bathrooms are typically extract only, and end up cooler. Most people like to have their kitchen and bathroom warmer than their bedrooms tho’ (i.e. the other way around).

    Still, the standard doesn’t mandate this “heat-using-the-ventilation-system” arrangement at all (it’s just a suggestion), and many passivhauses are built without it.

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