How Do You Save Energy and Reduce Emissions in a British Home?

Building in Britain is so different from North American house construction. A few years ago when I toured Ben Adam-Smith's self-built Passive House I couldn't figure out what was going on with the "beam and block" floors or the cavity walls, and I am an architect who has built a lot of houses.

Recently, the Eco Experts, a company in the U.K. that helps homeowners "find eco-friendly solutions" pitched a story about things people could do to improve their homes. "Using the most common UK home type—a semi-detached, three-bedroom house (31.4% of UK housing)—we’ve calculated the average implementation cost of 8 popular carbon-saving domestic technologies and the savings on CO2 emissions/energy bills a UK homeowner would save yearly and over 20 years."

Their timing is propitious; British heating costs are soaring, and just as this post was being written, the Chancellor of the Exchequer (not really equivalent but closest in the U.S. to the Treasury Secretary) announced tax cuts for what a previous Prime Minister called "all that green crap."

Author Beth Howell provides a lot of information and backup so there was a lot for me to chew on, and I asked questions of a few experts in the U.K. to get their thoughts.

The eight carbon- and energy-saving technologies discussed here are similar to those we have discussed in North America, described by Elon Musk as "the future we want"—solar panels on the roof, batteries, and an electric car in the garage. It's about adding stuff and, to be fair, the Eco Experts are in the business of putting the buyers and sellers of stuff together.

I have never been a fan of buying a lot of stuff, having learned from green building pioneer Harold Orr, who figured all this out almost 50 years ago, that 30-40% of your heat loss is due to air leakage. So the first thing you do is a blower test and then you get out the caulking gun and fix that. When asked about this, Beth Howell told Treehugger:

"The UK does do blower door tests but they are not a construction requirement (and therefore less common) compared to most of the United States, where blower door testing is a relatively new construction code requirement. Maybe we need to include a section on it in the future!"

Sustainable building writer and consultant Kate de Selincourt also told Treehugger: "I agree that it is missing the fabric first approach pretty conspicuously, sadly the 'buy some bling' is very much the mainstream understanding of eco-renovation here."

The other main point I had questions about was the cavity wall insulation, which was surprisingly cheap. Cavity walls are made up of two parallel walls of masonry with a gap in between; from a North American perspective, it seems like a weird way to build. Kate de Selincourt tells Treehugger that "cavity walls are indeed weird, sometimes insulation works well (and pays back well) but you need a reputable installer who will check it isn't going to track a load of driving rain into your internal walls."

Beth Howell explains that "the Centre for Sustainable Energy states that professional installers can carry out cavity wall insulation very quickly (in about two hours), with no mess. It also states that the most common material used in cavity wall insulation these days is polystyrene 'beads', which can be inserted easily and far into the cavity, reaching awkward areas without the need to drill lots of holes in the wall." The link she pointed to shows them drilling holes from the outside and squirting the beads in.

Then there is the heat pump. We have discussed them at length, most recently in the post, "What do we need more: Insulation or Heatpumpification?", which was about the debate over whether you add stuff (heat pumps) or fluff (insulation). It is the game changer that lets people do a more cost-effective renovation and still get off natural gas and go carbon-free.

Roof insulation is an obvious no-brainer, relatively cheap and easy and very effective. The double-glazing of windows is something I have always described as not being worth the money, and I continue to think that smart thermostats are dumb.

But the one thing that really excited me about the Eco Experts' website is that they supplied real data: the average cost, the break-even point when savings exceed initial purchase cost, and the savings of energy and CO2 over 20 years so that I could figure out what gave the most bang for the buck or pow for the pound. So I threw all their numbers into a spreadsheet and sorted it by pounds per ton of CO2 saved.

What is immediately clear is that fluff beats stuff. Window replacement gives by far the poorest return on investment for carbon savings, with solar panels and batteries next. The air source heat pump is expensive per ton saved, but it saves a lot of tons, and that was the point of the exercise. The smart thermostat delivers the most pow for the pound, but not that many tons. Fluff, or insulation, delivers the most. Here it is in graph form:

I would love to see what air sealing and a proper heat recovery ventilator would do to this, but as Kate de Selincourt tells Treehugger, "The UK generally has no clue about the value of airtightness, or how to do it, or how to ventilate properly once you've done it. British homes are generally muggy and heavy with the pong of 100 perfumed domestic products, it's grim."

According to the Eco Experts, the British Government is giving out grants for heat pumps and car chargers. When the Canadian government rolled out a grant program recently, they made blower door tests and professional recommendations mandatory before they gave out a dime, noting:

"Your home operates as a system. All of its elements—the walls, the roof, ventilation, heating and cooling systems, the external environment, and even the activities of the occupants—affect one another. How these elements interact determines your home’s overall performance. For example, poor insulation or ventilation can cancel out an investment in new windows or doors. It is always advisable to consider building envelope measures as the first part of your retrofit journey."

The Eco Experts have provided a valuable service by letting people see the comparative costs of the stuff and fluff that can turn a home into an eco-home. Perhaps another service they might add to their business is to go out and visit with a blower door and an infrared camera and tell people what they really need to save money and reduce carbon. The results might be surprising.

Get more information and the full infographic at the Eco Experts.