John Butler tells the story of how he retrofitted a bungalow to be more energy efficient. Having carried out a lot of the work himself, he also shares what he's learnt about airtightness and overheating.
Interview with John Butler
Although it had been John and Anna’s dream to build their own house, they found themselves muscled out of the local market for plots by builders.
John had attended a straw bale building course and was struck by some of the slides which showed a bungalow in the Czech Republic which had been wrapped in straw bales on the outside. With plenty of bungalows in the local area with poor energy efficiency their focus shifted away from the idea of building from scratch and instead towards searching for a property to retrofit and extend.
Straw was Always Part of the Plan, Whether for a New Build or a Retrofit
Having been on straw bale building courses and volunteering on builds, John felt that straw was a fun material and enjoyed the atmosphere on site from the types of people it also attracted. The more involved he got the more he realised its sustainability potential; being well insulating, breathable, accessible and a waste product from agriculture.
Gaps Need to be Eliminated Between the Bales and the Original Walls When Wrapping the Building Externally
Firstly the walls were levelled with clay to ensure no rodents or insects were able to crawl through the channels. Gaps would also potentially allow air flows which would bypass the insulation. Once the walls were level they were able to create a firm connection for clamping the bales onto.
Foundations Were Needed for the Bale Walls
As John was trying to avoid using concrete foundations they dug down and used gravel, compacting a layer, before adding further layers by the same method and finally finishing up with a strip of limecrete. The bales themselves were elevated from the ground by an insulated plinth brick wall to ensure that any moisture or leaks would run through the bales and drain out through the foundations.
Airtightness Should be Planned From the Beginning
Unfortunately airtightness was something John only became aware of later in his project! He discovered the importance of airtightness for energy efficiency through following others on social media, and then tried to incorporate it into the build. It was easier to do this in the extension, but in the bungalow they also managed to use tapes around the windows and are hoping that the plaster skim will keep it airtight. An air test they carried out before completing the finishes showed the weak areas and where they needed to go back and make adjustments.
John admits that with hindsight he would have planned better and carried out more research before starting, to ensure he had a really good airtightness system. He notes though that he would be interested in finding out about the sustainability credentials of the tapes and membranes themselves.
Initial Plans Were Designed and Drawn in Sketchup
Once John and Anna had thought about the spaces they were looking for in their new home, John drew their ideas in Sketchup before sending them to their consultant in the Czech Republic for suggestions.
A Vaulted Ceiling in the Living Area Helped Compensate for the Loss of Height From Insulating the Original Floor Slab
One option would have been to excavate the original concrete slab, however with the waste materials being sent to landfill and the risks of excavating within an existing building, it probably would have been wise to have knocked the bungalow down.
Instead, the chosen option was to use wood fibre insulation boards on top. This does mean however that they’ve not managed to get enough insulation in the floor, without digging the concrete slab out, for it to reach Passivhaus standard.
Solar Tubes and Roof Lights Provide Welcome Additional Light, But Have Their Drawbacks
The solar tubes have been effective in providing additional light without structurally taking up much roof space. In summer however, they have found that the direct sunlight beaming through their various roof lights has resulted in overheating of the spaces. This is something they had prepared for on the living room’s two large roof lights and installed external shading, however this does mean that using the shutters blocks the light from coming in.
Again, with hindsight John would have planned for this and used the PHPP (Passive House Planning Package). It is an annoyance for John that they had planned for saving energy and not being cold in the winter, but now have the opposite problem of overheating in the summer.
Self Building Has Been Satisfying But Draining
While John finds it very satisfying to point at the work he has done himself, he readily admits that it has also been all encompassing and draining. He recommends having people to help out at least with elements of the build to provide stimulation and motivation.
He sees self building as a balancing act, of paying people to do the labour meaning you could get back to work earlier, against the potential financial savings and satisfaction of doing the work himself.
The result is a house where he and Anna are enjoying their new light, warm and comfortable spaces.
Find Out More
The Future of Housing – Premiere!
The date is set for the first screening of our documentary The Future of Housing – And How Airtightness Can Help.
This project was crowdfunded on kickstarter earlier in the year and on Thursday 4th December 2014 you can see what we've been up to!
The venue will be the Mildmay Community Centre, which was the UK's first non-domestic retrofit to the Passivhaus standard. So there's a building to check out too!
We hope you are able to join us for what will be a special evening. Capacity is limited, so get your ticket now.