Diy Conservatory Heat Loss

Calculating the heat lost from your conservatory
It isn’t difficult to calculate the amount of heat lost from a conservatory or home, it is just a matter of measuring up the rooms and doing some simple arithmetic. It will help if you can prepare a simple sketch plan of each floor on which you can write down the dimensions.

First, the ground floor needs to be measured and you can do this by adding up the area of each room on the ground floor that is heated. No need to measure upper floors unless they are over a garage or open space below. Similarly only the outside walls and their window and door openings need to be measured and the areas of each recorded, not the internal walls, unless they separate a room from a garage or other unheated space.

The roof is where most of the heat leaves from and its area should be measured. This is most easily achieved by using the floor area, if the roof is insulated at the ceiling level. If it’s insulated at the sloping rafter level (as in a room-in-the-roof situation) the floor area on plan can be converted to the slope area by trigonometry or, in the absence of your school exercise books and a calculator with a cosine button, by using the factors below.
If you have different types of wall, window, door, floor and roof, the area for each type needs to be measured separately. For example, double-glazed windows and single-glazed windows or insulated cavity walls and solid walls: each type will have its own rate or heat loss known as its U value and this value needs to be established and multiplied to the area to work out the total heat lost from that element.

Obviously there will be a larger amount of heat lost from the conservatory-extended home than from the existing home and if you can present enough information to the Building Control Officer to show the overall heat loss is minimal you may be able to persuade him.You can add some insulation to your existing home to counteract the conservatory, reducing the percentage heat loss: extra loft insulation, replacement windows or cavity wall insulation are all worthwhile remedial measures.

If this isn’t enough, the calculation could be extended further by calculating the conservatory extension with the “notional” equivalent in an ordinary extension that complies with the insulation (U) values required. These values have been increasing periodically over the years and will need to be checked as to current values. In this calculation you will be assessing what the heat loss would be if you built your conservatory to the same size but with the maximum allowed areas for windows and rooflights that a regular living area extension to your home would have. In 2004 for example the guidance allows up to 25% of the floor area in window area and so you would calculate the total wall area of your addition and take one quarter of it as glazed to be multiplied by the required U value for glass and the rest for walls, multiplied by the minimum required U value for walls. In doing this you create an imaginary addition that is the worst in terms of thermal insulation that the regulations will allow you to build.

Once you have this information you can compare your existing home as it stands today with the one you want to build (and the percentage of added heat loss) and the existing home and the one the Building Regulations would allow you to build.

The difference between those two percentage increases may now be small enough to convince your Building Control Officer that your proposal is reasonable. You can see that even a fully insulated normal extension is allowed some glazing for windows and doors, and will (simply because it makes the home bigger) be losing some extra heat anyway. In this respect it might be necessary to reduce the size of your conservatory if you want it to be open-plan with your living space.

Where this approach is less convincing is where your home is relatively highly insulated already, such as a new home that can’t be improved upon and any conservatory addition will look bad in comparison. If you fall into this category your only hope may be to have an “energy grade” produced for your home as extended and compare it to the energy grade on your existing home. For that you need a Standard Assessment Procedure or SAP rating.