I wonder if anyone might comment on the relevance of either BREEAM or NHER ratings to an assessment of whether an installed heating system fulfills the minimum NHBC Guidelines for space-heating, i.e. that: 'The main living room of a dwelling should have a heating appliance or a heat output as part of a central, or whole home, heating system which is capable of maintaining a design temperature of at least 21°C in the room when the outside temperature is -1°C.' <source: the dimplex-resource.co.uk website>
I realise that both the BREEAM and NHER assessments prioritise environmental considerations, insulation criteria, energy efficiency, and CO2 emissions, and that it may not be their principle concern, if they are concerned at all, to evaluate the actual internal effectiveness of the heating system, although the BREEAM assessment does seem to concern itself broadly with the 'health and well-being' of prospective occupants.
Last edited by mjones003; 31st August 2008 at 20:16.
Reason: mistake
The rating considers the whole house not just one room. As well as that it is calculated assuming everything has been built correctly.
There is a mathematical formula to work out if there is sufficient heat input into a room. Considerations are
Heat loss – assuming that the construction has been built as per the drawings the walls, floor and ceiling will prevent heat being lost through the fabric at a given rate for a given temperature.
Heat input – the heat emitter will give out a certain amount of heat for its size as long as the boiler is large enough (it normally is)
If the calculation is done to say the heat emitter is large enough for the room there is something wrong. The British Standard now allows for -30C outside.
Problems
Insulation is missing from an element of construction. This could be the wall especially if it is blown fibre.
The thermostat is positioned incorrectly or the radiator within the vicinity of the thermostat is wrongly balanced. This would make the thermostat tell the boiler to stop producing heat while the lounge is still cold.
When calculating the heat output of the radiator it is reliant on the temperature reaching the radiator being correct.
The builder may offer to put in a larger radiator to overcome the problem which it may do but it will not solve what the actual problem is.
Thanks for the reply. I am interested in what you say about thermostats. In a small new-build property featuring only wall-mounted convector-heaters as the sole heating provision, with thermostats integral with the heaters, the system does not appear to be capable of meeting the guidelines, due to the behaviour of the thermostats cutting off the heat when the heater itself is hot, but before the room is comfortably warm. This was the case in March at least, when the outside temperature was generally above freezing. To redesign the system employing room-thermostats would seem to offer an obvious solution.
Both the BREEAM and NHER/SAP assessments do not seem to be prescriptive about the functional components of the heating system. In fact they both seem to assume that sufficient heating will be employed, even when it may be absent during the assessment. The building regulations (Part L) are neither prescriptive about the requirements of thermostats in such an installation, specifying only the choice of room-thermostats or integral ones.
In raising this issue as a complaint with the property provider, they have used the SAP rating (81/120), and BREEAM rating (Very Good) in defence of the heating system, but, according to the limited research I have been able to do on the subject, which is summarised above, this does not seem to be justified, and is perhaps being used as an alibi.
I am conscious that professional building assessment organisations may often function in supporting builders and property providers against residents. The NHBC themselves do not seem to be prepared to comment on the enforcement of their own guidelines. I am wondering therefore which authority I could appeal to.
Problems
Insulation is missing from an element of construction. This could be the wall especially if it is blown fibre.
This is a common problem and also rooms over garages may not have adequate floor insulation. It is difficult to determine as you either have to look inside the wall/floor or get a thermal imaging company in. Link in this thread
I don't think it's likely to be an insulation problem as it is a new-build property, which has attended fairly thoroughly to insulation properties. It is not a heat-loss problem, but one of insufficient heat-input, due to the action of the heater thermostats cutting off the heat prematurely. This might be difficult to establish according to power-output/heat-loss calculations, as, on the technical data these might appear to be in order - the calculations do not anticipate the action of the thermostat cutting off the heat because the heater itself is hot, and maintaining the heater off for extended periods while the ambient temperature drops significantly (the heater itself remaining hot and making the thermostat unresponsive to drops in the ambient temperature).
The trouble with electric heaters is that they do tend to keep cutting out and give out a lot of heat in a short time then they cut out. If they are not functioning correctly the NHBC are obliged to provide the resolution service as part of the policy they have with you. If they don’t allow you the opportunity of requesting a resolution it would be very unusual. Have you written to NHBC yet?
Well, no I haven't as I am a tenant, not an owner. However, I thought I'd use the forum to explore the issue. I have raised a complaint with the landlord, who may themselves have a policy with NHBC. Are you aware of any documentation on the problem? Such a heating configuration certainly complies with the building regulations, and BRE and most EAs don't seem to take it into account, as in terms of power-output/heat-loss calculations the problem does not appear. Despite this, I am certain that this system will not comply with the NHBC guidelines in terms of heating performance.
New Homes News 
NHBC Guidelines for space-heating 
Heat loss 
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