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
Windows
Doors
Extension
50mm stone flags
50mm glass fibre plus 25mm plaster
Double glazed
Solid wood
Description
Cavity wall ,stone outer , block inner wall
U value table
U value
Watts/m 2 /k
1.85
0.7
Wall( House) 600mm solid stone wall plus plaster skim 1.78
2.78
0.64
1.33

House
Element
Area
M 2
U value Watts/K
Floor
Roof
113.5 1.85
113.5 0.7
Wall 411.66 1.78
Windows 39.3 2.78
Doors
Air exchange
Total
85 3
243
92.5
411.66
109.3
25.5
177
1040
Bridgefield Heating calendar notes
2%
10%
1.
Central Heating off June, July, Aug and September
2.
Use central heating 9 hours per day
3.
Degree days value adjusted for months of central heating use
4.
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

1.
Improve Loft insulation by increasing to a minimum of 200mm
2.
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.
3.
Stone and masonry integrity on end wall gable as escaping heat shown on IR photographs w could be due to perished mortar.