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How to build an energy-positive house at affordable prices?

Energy positive houses have been on the rise across Europe. What was a luxury for rich and environmentally aware customers is now penetrating the middle layers of the market. While some devices and building methods remain out of reach for the average household, some others have become quite accessible.

It was only in the middle of the year 2015 that the first energy positive house (1) appeared in the UK. Heavily covered by media, the construction was more a showcase, designed at enticing various types of replication, than housing per se - although it was indeed designed for it. In that sense, the project met success, because an increasing number of companies are offering new ways to push down the energy needed to heat and operate your house, while pushing up the energy your house is able to produce, to the point that your connection to the power grid will no longer be used to draw power, but to funnel more power into the network - with a little extra cash for you.

So technologically advanced it must be financially out of reach? A few years ago, perhaps, but not today. Here are a few affordable ways to achieve the feat. The first aspect to address is the insulation: thermal leaks in the house will cause the energy needs to skyrocket. The problem here is that two separate sets of material are often used to create the walls: cement for the structure, and an additional layer of insulator. The French company Logelis has found the way to integrate both layer into one, with 100%-recyclable polyurethane walls and cement structure delivered at the construction site and fitted into place like high-tech legos. Not only will these walls provide the house with solid structure and top-notch solidity, but it also greatly reduces the cost of construction because all the plumbing and electric wiring is built into the panels - killing off the extra expense of calling in plumbers and electricians after the first construction phase. And so, Logelis promises “less than six months of construction time, for a price 15% inferior to the overall price of a traditional house, thanks to workforce expenses lower than the competition’s, by 30 or 40%.” How’s that? Renaud Sassi, CEO of Logelis, explains: “We lay a panel, and then a post, and so on… everything is fixed to a wooden frame. In ten days, the house is airtight and watertight. It is surprisingly simple”.

Also, if you are building your home from scratch, use the opportunity to choose your foundations wisely. Passive slab insulation professionals (2) can reduce the heat loss from below in different ways: “Internal load bearing walls are built on a thickened slab on EPS300 so there are no external or internal footings. It’s much quicker to install a Passive Slab, so labour costs are reduced by 20%. 60% less concrete is required because there are no footings or screed to pour, so the concrete is poured only once. This lowers the carbon footprint of the house. The unique shape of our Passive Slab foundation elements delivers a high yield from a block of EPS, cutting down substantially on waste.” So, all in all, it may not be any more expensive than traditional foundations, and even if it is, the difference it will make in the long run will make it worth the small extra investment.

Then, of course, comes the choosing of power production methods. Firstly, if you want to keep control of your budget, forget about the obvious solar choice. Colin Dunn, from the Treehugger foundation (3) warns “ The downside, at least for now, is the cost: it is rarely cost-effective to power an entire home entirely with solar, even allowing for several decades for a positive return on the investment. Add to that the wide variance of solar exposure by location and the fact that solar only works when the sun is shining, and it’s easy to see why solar remains a part of the answer, and not the whole thing.“ Given the price of solar panels, the scarcity of direct sunlight in many parts of the UK, and the instability of electricity prices, solar panels would probably be an expensive gamble. He also warns against wind turbines, which can prove unprofitable and outright expensive : “: if the wind doesn’t blow, the turbine stays still and the electricity isn’t generated. Wind turbines also have moving parts, which means more things that require maintenance and have the possibility of failure. But if you’ve got a good consistent stiff breeze blowing through the back yard, you can harvest its energy for years to come.” Indeed, if you have the right conditions met on your land, these options may be profitable in your specific case.

Take a look on your land to see if a stream is running through. If so, you’re in luck: you now have access to the cheapest, and most reliable way to produce power. Energy alternatives states (4) “Our experience with micro hydro systems has demonstrated that water power will produce between 10 and 100 times more power than PV or wind for the same capital investment”. No wind interruptions on your turbines, no nights to put your solar panels to rest, pure regular power production, for a low price.

One can expect many more innovations in years to come, to make energy positive houses a reality for the masses. Governments across Europe are funding eco-friendly research, and even power producers look kindly upon small energy producers. In all likelihood, performances will increase over the next few years, and prices will drop, mechanically making house construction a more environmentally friendly business.

1. https://www.theguardian.com/environment/2015/jul/15/britains-first-energy-positive-house-opens-in-wales
2. http://viking-house.ie/passive-house-foundations.html
3. https://www.treehugger.com/sustainable-product-design/generating-off-grid-power-the-four-best-ways.html
4. http://www.energyalternatives.ca/SystemDesign/hydro1.html

This was posted in Bdaily's Members' News section by Emma Miller .