Further Guidance
The exposed perimeter of a ground floor is the total length of the external wall dividing the dwelling ground floor from the external environment or from an unheated adjoining space. The part of the dwelling perimeter that adjoins (for example, by a party wall) other heated properties (residential or commercial) is not included.
For example:
The floor U-value is calculated according to I.S. EN ISO 13370 using its area and exposed perimeter and rounded to two decimal places. The ratio of floor perimeter to area is the P/A ratio. The following parameters are used:
For solid ground floors:
For suspended floors:
Note that non separated conservatory floors are to be treated as normal floors within the dwelling.
| Age band | All-over floor insulation (for solid or suspended floors) |
|---|---|
| A, B, C, D, E | None |
| F or G1 | 12 mm |
| H or I | 35 mm |
| J | 50 mm |
| K | 94 mm |
| L | Not applicable – Backstop U value applies |
This table also applies to heated basements or ground floors above unheated basements.
For Age band L no assumption is made on the thickness of insulation installed. It is assumed that the floor meets the requirement of maximum Area-weighted Average Elemental U-Value specified in the applicable revision of TGD L 2011. In the absence of the as-built U-value from the BER issued at date of dwelling completion, use a default value.
Table 2.7 sets out the age-band ranges
1 - If the dwelling is of age band F or G but the roof of the dwelling is shown to have no insulation, then all floor types must be assumed to be age band E (no insulation) where contrary evidence is not available
| DEAP software tab: “Building” | ||
|---|---|---|
| Building: floors | ||
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Guidance on re-use of data for floors can be found here |
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| Data Entry Item | Guidance | Documentary Evidence |
| Storey heights | Relevant floor-to-ceiling heights should be measured on site (or taken from drawings for provisional ratings). Floor thicknesses between storeys should be taken from drawings where available, measured on site, or may be taken from defaults, particularly for existing dwellings. | Sketches/drawings showing relevant dimensions |
| Living area | Follow DEAP Manual guidance using living area recorded in dwelling sketches or architectural drawings. | Sketches/drawings showing relevant dimensions and room types. |
| Floor areas | Dwelling sketches or architectural drawings must contain details of floor dimensions. | Sketches/drawings showing relevant dimensions. |
| Room in roof floor areas |
Dwelling sketches or architectural drawings must contain details of floor dimensions. The DEAP Software can be used to auto-calculate room in roof heat loss areas for existing dwellings. |
Sketches/drawings showing relevant dimensions. |
| Heat loss floor U- values |
It is unlikely that there will be enough visible information available on site to support a non-default u-value. In general, the main evidence to record during the site survey (for default and non- default floors) are the area, perimeter lengths and relationship to adjoining spaces (exposed, semi-exposed, heated, etc.). These variables must be recorded or available on sketches/drawings as appropriate to the floor type. Non-default U-value Where sufficient supporting evidence is available a non-default U-value must be used following the guidance provided in this guide. A U-value calculation is mandatory for non-default floor u-values. When using documentary evidence, the documentation must indicate the type and thickness of installed insulation and other layers in the building element and that the entire heat loss surface has achieved the non-default U-value. Default U-value Where there is insufficient information available to calculate U-values, then defaults from should be used. |
Sketches/drawings showing relevant dimensions and adjoining space type (e.g., heated/exterior/unheated). For non-default U-values:
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