Trystan Lea

Assessments: Bothy

Published: 5th July, 2018

As well as working on our own home. The following assessments & calculations repeat a similar process for other projects, primarily family. I will be uploading the calculations and results of projects undertaken here over time.

The primary aim of the following calculation is to work out the radiator sizing for expanding the existing heat pump into the older part of the bothy. I also explore breifly the potential for more ambitious work on improving building fabric and air-tightness.


Calculation notes:

Heat loss calculation:

Room by room heat loss calculation is based on the MCS Heat Pump Calculator that implements the EN12831 heat loss calculation standard.


Without work to improve the building fabric, it looks like the addition of one Dimplex SmartRad SRX180 and one 1200x600 double panel convector to the existing heat pump system would be sufficient to achieve 18-21C in the old part of the bothy during the relatively rare occasions that outdoor temperatures reach -3C. The total heat requirement would however push the 5kW ecodan heat pump to its limit during these times. The old part of the bothy does have a ClearView wood stove which could be used to topup the heat requirement at the coldest times.

Retrofit notes

In the long term it would be better to improve the building fabric in order to reduce the space heating requirement. Entering the following U-values and ventilation rate in the calculator above suggests a potential to reduce demand by 45%:

The cumulative effect of these measures would be to reduce space heating demand and the maximum heat requirement by ~45% to 7318 kWh and 2535W respectively.