Case Study Bridgefield Farm


Case Study Bridgefield Farm

House description

Bridgefield was built about 1873 and employs 600 mm solid stone walls, the floor is paved in solid stone slabs with all widows double glazed. The prime heating fuel is oil supplying an oil fired central heating boiler and also an ‘aga’ stove with heats the downstairs hot water cylinder. Secondary heating to some downstairs rooms is provided by a multi solid fuel stove.

Outside dimensions

38ft by 35ft by 18ft with 2 ft walls internal size is 34ft by 31ft by 18ft = 537 cu metres

Air Change heat loss

177 watts/k based on 1 air change per house volume per hour

House fabric calculations

House Element Floor Roof Wall( House) Windows Doors Extension wall

Double glazed Solid wood


50mm stone flags 50mm glass fibre plus 25mm plaster 600mm solid stone wall plus plaster skim Cavity wall ,stone outer , block inner U value table

U value Watts/m 2 /k

1.85 0.7 1.78 2.78 0.64 1.33

House Element

Floor Roof Wall Windows Doors Air exchange Total



M 2 U value Watts/K

113.5 113.5 1.85 0.7 411.66 1.78 39.3 2.78 3

Bridgefield Heating calendar notes

243 92.5 411.66 109.3 25.5 177 1040 2% 10% 1.




Central Heating off June, July, Aug and September Use central heating 9 hours per day Degree days value adjusted for months of central heating use 1 litre of heating oil gives 10.3 Kwh 17% 23% 39% 9% Calculated W/K value for Bridgefield × degree day value ×hours of use ÷1000 = yearly Kwh 1040 ×2200 × 9 ÷1000 =20,592 Kwh per year for room heating Assume 70% efficiency boiler = 29417Kwh or 2856 litres oil for room heating Water heating is approximately ¼of heating value =714 litres Sub total 3,570litres of heating oil Aga stove and downstairs hot water cylinder uses 10 gallons per week =2392 litres per year

Calculated Total oil usage at 5962 litres per year

IR photographs

floor roof walls windows doors air exchanges





Improve Loft insulation by increasing to a minimum of 200mm Improve hot water tank insulation and if possible try and employ a switched diverter system to use spare heat generated by ‘aga’ to heat existing 2 nd hot water cylinder. Stone and masonry integrity on end wall gable as escaping heat shown on IR photographs w could be due to perished mortar.