HBDesignGreenHome_SCa

How to Design a ‘Green’ Home

All too often sustainable solutions are used only as a means of reducing energy bills. Charlie reveals how these features could improve the quality of spaces too.

For most, the driving force behind building a low-energy home is saving energy and, therefore, money. Undoubtedly the idea of saving the planet comes into it, but the reality comes down to low energy bills.

My design work is focused on new builds, extensions and refurbishments, all driven by a desire to be as sustainable as the client, brief and budget will allow. Through this I’ve come to believe that the reason for the take-up of sustainable building techniques is solely concentrated on money saving and payback, but people should instead be investing more in airtightness, insulation and triple glazing to create quality spaces. Still, calm, healthier and quiet — properly built, low-energy spaces are far nicer places to live. Once you’ve experienced low-energy housing you will never want to live in a draughty, cold old house again.

Comfortable, good for wellbeing, lower bills and doing your bit to conserve the planet — it sounds too good to be true. The downside is that while cheaper in the long run, low-energy construction costs more upfront. There are, however, some simple sustainable design principles that can be adopted to help make your home green.

Smart Design

One of the best things to come out of the eco sector is thermal modelling. This is the ability to use computer programmes to test the energy, thermal and water performance of a design as it evolves, and allows designers to optimise a building’s shape, orientation, windows and insulation to passively use the sun to do as much heating and lighting as possible. It goes hand-in-hand with a fabric-first approach rather than focusing, as many do, on how to heat the house through low-carbon technologies such as heat pumps, photovoltaic panels or biomass boilers. I would never design a new house without using thermal modelling to inform the process.

Overheating

All these homes with large south-facing windows and lots of insulation are wonderful, but many new builds suffer from overheating. With our climate set to warm considerably over the next 50 years this is only going to get worse. Test your home for possible overheating at the outset using thermal modelling and design it out at an early stage.

Size

The bigger the house, the bigger the bills (we calculate energy consumption through kW/m2/annum) — so try to make internal spaces work harder for you rather than just creating more rooms. Small can be beautiful and this will allow you to spend more money per m2 to get better quality spaces.

Insulation

It certainly isn’t sexy, but to create super comfortable low-energy homes, insulation is your biggest asset. Critically we are not talking about a few tatty layers of fibreglass in the loft — we are talking a minimum of 300mm-thick insulation which is properly installed. It is a case of insulating as much as possible, and then some more!

Cold Bridges

The key to insulation is lots of it, but you must also have total continuity. Any gaps or bits of structure (lintels, masonry, timbers) that bridge the insulation layer not only lose heat but moisture condensates on the resultant cold spots too. This often leads to mould – a big health risk – so you have to be very careful that your insulation layer is carefully designed.

Windows

Windows are important to get right, especially as they are replaced so infrequently. A house will usually go through multiple boilers before any of the windows are replaced, so opt for triple glazing for new builds and at least double glazing for existing homes. It is not just the quality of the windows, but how they are fitted is equally important. Air leakage around windows is a big problem and using the right foams, sealing tapes and fixings is critical.

Airtightness

After insulation, airtightness is vital. This means sealing up all the gaps and holes in your building. Draughts and air movement within a dwelling have a huge impact on the comfort of a home. The perfect internal temperature for most in a well-sealed, draught-free house is 19°C, but if there are draughts then achieving 21°C is required for a comfortable temperature. This seemingly small rise in temperature will have a big impact on your comfort and energy bills.

Heat Recovery

After a house has been highly insulated and sealed, the biggest source of heat loss will be ventilation. People need lots of fresh air to be healthy and to provide this and maintain airtightness you need a mechanical ventilation heat recovery (MVHR) unit. This is a system that extracts warm, moist air from bathrooms, kitchens and utilities by passing it through a heat exchanger to preheat fresh air from the outside which is then pumped into the bedrooms, sitting rooms, etc. It provides up to around four times the ventilation rates in a normal home and filters the air for dust, pollen and pollutants. In a well-insulated airtight house it will halve energy consumption and give fresh, warm clean air — it’s one of the best bits of technology to come into the low-energy sector.

Air Quality

In terms of creating low-energy, comfortable but also healthy homes, good internal air quality is crucial. MVHR systems help by upping the ventilation rates, reducing moisture and filtering air that comes into the house, but I am also always very careful to try and specify low toxicity and low off-gassing materials. My rule of thumb is that if I would eat my dinner off it, I will put it in a house! Think about reducing the use of MDF, particleboard and petroleum-based products and consider materials with low toxin levels instead.

Stay Positive

It is easy with all the additional complexity these issues bring to lose sight of the fact that your house should be joyful and inspiring. Sometimes low-energy architecture can become a little too worthy and rational. You need a bit of magic and sparkle in a project — don’t let low-energy concerns kill that. Whether you’re dealing with a new build or refurbishment, low-energy homes are not easy to achieve but once you do it, you’ll never go back. Super sleek £50,000 kitchens and cinema rooms are the luxuries of today; low-energy homes are the luxury of tomorrow.

  • IMG_9624 08/12/2017Innovative Insulation At our own project here in North Oxfordshire, we’ve employed a clever technique for insulating the outside. This involves creating a continuous layer of insulation therefore reducing thermal bypass. More details can be found here on Charlie’s Blog at Homebuilding & Renovating , along with other posts
  • NaCSBA RTB 27/11/2017Right to Build Summit This Thursday Charlie will be a guest speaker at the NaCSBA Right to Build Summit being held at the NSRBC in Swindon. The summit provides a unique insight in to the current and future prospects for the custom and self-build
  • Akeley night 20/11/2017Re-imagining the Focal Point We were approached by Akeley District Church Council to provide sketch design ideas for an unheated open ‘pavilion’.  Akeley Church was demolished in the 1970s after a disputed structural survey deemed it unsafe. Ever since then church services have taken place in
  • Pressure testing 14/11/2017Air Tightness We endeavour to design and detail buildings with a high level of airtightness. Having an airtight house means that its thermal performance is much more efficient with the warm air being unable to escape through the building fabric. It’s still very
  • IMG_5914 07/11/2017Decisions Decisions Amongst other things, a building project presents a constant stream of decisions. Paint colours are one of the more pleasant but nonetheless important ones. At Ambury Barn the builders have been working carefully to convert the open expanse of the
  • graven hill 31/10/2017Graven Hill This coming Saturday 4th November, the Graven Hill Village development are unveiling their next phase of plots. Charlie will be there amongst other industry experts and the Graven Hill team for the big reveal of Phase 1B. Graven Hill is
  • IMG_5350 copy 24/10/2017Taking shape The old bungalow walls of this extensive renovation have been waterproofed and a new external skin of Cotswold dry stone walling is going up. Not forgetting the insulation, airtightness membrane and taping of course!  
  • Version 2 19/10/2017Walking through the floorplan Beanacre is now out of the ground. The floor slab is down, the structural walls are going up and this means it’s possible to get an idea of how the spaces will ultimately work together. Check the Homebuilding & Renovating website blog where Charlie meets with
  • IMG_5296 16/10/2017Getting started It’s always exciting when a project starts on site. Here the intention is to retain the existing 1960s form and extensively remodel the interior. Load bearing walls have been removed to open up the interior and make once unusable spaces usable
  • You&Yours 13/10/2017You & Yours Catch Charlie on BBC Radio 4’s consumer affairs programme You & Yours today at 12.15pm, where he’ll talk about the trend for improving your home rather than moving home.
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