How can I super insulate my walls - part one: foundations - The Oxford Green HouseThe Oxford Green House

We first considered external wall insulation with render then, because our neighbours were concerned about the change from brick walls and wouldn’t give us permission to do the back wall of our house, we switched to internal insulation throughout. The more we looked at internal insulation the more concerned we were with:

Loss of floor space
Loss of thermal mass
Increased risk of interstitial condensation (in the walls)

Steve Harris suggested we build a new brick wall around the house to form a second cavity. The benefits of this approach are:

No loss of floorspace
Thermal mass of existing walls preserved
Much reduced risk of interstitial condensation

Some of our neighbours were concerned about introducing a step into the front wall so wouldn’t give us permission to build a new wall at the front of the house. The new external wall is limited to the back and side with internal insulation planned for the front wall.

Start on site:

Mike, Jordan and Connor

We couldn’t get a skip on site so decided to bag up the soil to make it easier to transport. We thought about using a micro digger but given the lack of space and obstacles decided it would be better dug by hand.

Digging the foundations by hand

To speed up the digging we hired an electric breaker to loosen the soil.

Rather than buy rubble sacks we approached a local farm to see if they had any spare sacks. They were delighted for us to reuse the plastic feed bags as they otherwise pay to have them recycled.