Sustainable Homes Scotland
When is the test needed
Does your building need testing?
All new dwellings built under the new regulations will require testing prior to occupation. Building Control will identify the units to be tested. The sample size depends on whether ‘Robust Details’ have been used:
• If Robust Details adopted, test one of each dwelling type on each development. If any fail, do remedial work, test again plus another dwelling of the same type on same development
• If Robust Details not adopted, the number of tests to be carried out on each dwelling type on each development are as follows:-
• 4 or less dwelling types - test one of each
• Between 5 and 40 types - test two of each
• Above 40 types - test 5% of each. For each type, this can reduce to 2% if the first 5 tests are successful.
| No of dwellings of one dwelling type |
Number of tests to be carried out on each dwelling type |
| 1- 4 | one test of each dwelling type |
| 5 - 40 | two tests of each dwelling type |
| 41 or more | At least 5% of the dwelling type, unless the first 5 units of the type that are tested achieve the Design air permeability, the sampling frequency can be reduced to 2% |
Developments of two or less houses then a figure of 15 m³/m²/h can be used for the DER Calc and no test is required, alternatively if the same contractor has built the same design in the previous 12 months and can prove a compliant result then also no test is required.
Blocks of Flats have to be considered as separate developments, regardless of how many are on the same site.
Explanations
DER:
The DER is the calculated CO2 emissions (kg/m² floor area) calculated using SAP 2005
TER:
The TER is the Targetet Energy Rating.
Values:
The TER building assumes a q50 (air leakage) value of 10.0. If you use this as your design value (a cautious approach) the ventilation heat loss from your dwelling will be much the same as for the TER dwelling. As you have failed to deliver a 20% improvement here you will need to make it up somewhere else. If you proposal is a one or two dwelling development and you claim exemption from testing you will have to use a q50 value of 15.0, i.e. your ventilation heat loss will be significantly greater than that from the target dwelling. Making up for this is likely to be very challenging. The rationale behind this is fairly obvious: the ODPM does not want to encourage developers to claim the exemption, also human nature being what it is, it is very possible that quality control on site might be lessened when it is known that no test will be carried out (and vice versa).
BRE Survey of dwellings built to L1 AD 2002 (PDF) : Pressure testing a sample of dwellings gave the following results: Flats; range 3.2-12.4, mean 8.0; Houses: 5.6-16.7, mean 9.8