Mortgage for a Self build Passive House
We needed to borrow funds for a large chunk of the build but at the time we started construction (9 years after we moved in) we had paid off most of the borrowing on the initial house. Funding a new build is where a lot of self builders come unstuck as the criteria and cost of borrowing is not the same as for a normal mortgage. In the South East especially most self builders buy plots with small or dated housing stock on them that they intend to knock down and replace due to very limited availability of new building plots. From a lenders point of view there is then a period where the plot is worth substancially less than when purchased whilst the existing house has been knocked down and before construction of the new dwelling.
Most self builders need to use specialist lenders, and these tend to have higher rates and also often fix the flow of funding to stages of the build requiring a Surveyor or Architect to confirm when each stage is completed. I had heard very good things about Ecology Building Society self build mortgages and was delighted to find they would fund my build, not insist on staged payments and were happy with timber frame and timber cladding that most lenders saw as non standard construction. Most self build mortgages come with large fees from the Lender or Broker but the ones from Ecology were very small. At the time they had a lending criteria that I would have to demonstrate the design of my build would either be Passivhaus or have a SAP (an energy performance figure using approved software and methodology) score of 100 or more. They would then give a discount for the remainder of the fixed lending period based on obtaining Passivhaus certification or an as built SAP of 100.
I decided to opt for a SAP of 100 or more as this would be quicker and cheaper to complete than gaining Passivhaus Certification, and in the process my build could also be to Passive standards and then obtain certification later if I chose.
SAP Calculations
I undertook the design stage SAP myself with a free version of a professional software package as this did not need to be completed by a certified professional. It was a really beneficial exercise as I was able to easily play with performance of items of the build such as insulation and window values and see what effect they had on the overall score. It was rather disappointing to discover that solar P.V. panels have a much larger effect than good levels of insulation and airtightness on overall SAP scores and would explain why so many developments have a few token panels as they are a cheaper option than building the fabric of the building to a higher standard.