U-values apply to the entire area of the window opening, including both frame and glass, and take account of the proportion of the area occupied by the frame and the heat conducted through it. Unless known otherwise, double, and triple glazing should be taken as air-filled without low-E coating. If the U-value of the components of the window (glazed unit and frame) are known, window U-values may alternatively be taken from the tables in Annex F of I.S. EN ISO 10077-1, using the tables for 20% frame for metal-framed windows and those for 30% frame for wood or PVC-U framed windows.
| Glazing Description | Window with wood or PVC-U frame (use adjustment in Note 1) | Window with metal frame with 4mm thermal break (use adjustments in Note 2) | ||||
|---|---|---|---|---|---|---|
| 6 mm gap | 12 mm gap | 16 or more mm gap | 6 mm gap | 12 mm gap | 16 or more mm gap | |
| Double-glazed, air filled | 3.1 | 2.8 | 2.7 | 3.7 | 3.4 | 3.3 |
| Double-glazed, air filled, low-E (εn = 0.2, hard coat) | 2.7 | 2.3 | 2.1 | 3.3 | 2.8 | 2.6 |
| Double-glazed, air filled, low-E (εn = 0.15, hard coat) | 2.7 | 2.2 | 2.0 | 3.3 | 2.7 | 2.5 |
| Double-glazed, air filled, low-E (εn = 0.1, soft coat) | 2.6 | 2.1 | 1.9 | 3.2 | 2.6 | 2.4 |
| Double-glazed, air filled, low-E (εn = 0.05, soft coat) | 2.6 | 2.0 | 1.8 | 3.2 | 2.5 | 2.3 |
| Double-glazed, argon filled | 2.9 | 2.7 | 2.6 | 3.5 | 3.3 | 3.2 |
| Double-glazed, argon filled, low-E (εn = 0.2, hard coat) | 2.5 | 2.1 | 2.0 | 3.0 | 2.6 | 2.5 |
| Double-glazed, argon filled, low-E (εn = 0.15, hard coat) | 2.4 | 2.0 | 1.9 | 3.0 | 2.5 | 2.4 |
| Double-glazed, argon filled, low-E (εn = 0.1, soft coat) | 2.3 | 1.9 | 1.8 | 2.9 | 2.4 | 2.3 |
| Double-glazed, argon filled, low-E (εn = 0.05, soft coat) | 2.3 | 1.8 | 1.7 | 2.8 | 2.2 | 2.1 |
| Triple glazed, air filled | 2.4 | 2.1 | 2.0 | 2.9 | 2.6 | 2.5 |
| Triple-glazed, air filled, low-E (εn = 0.2, hard coat) | 2.1 | 1.7 | 1.6 | 2.6 | 2.1 | 2.0 |
| Triple-glazed, air filled, low-E (εn = 0.15, hard coat) | 2.1 | 1.7 | 1.6 | 2.5 | 2.1 | 2.0 |
| Triple-glazed, air filled, low-E (εn = 0.1, soft coat) | 2.0 | 1.6 | 1.5 | 2.5 | 2.0 | 1.9 |
| Triple-glazed, air filled, low-E (εn = 0.05, soft coat) | 1.9 | 1.5 | 1.4 | 2.4 | 1.9 | 1.8 |
| Triple-glazed, argon filled | 2.2 | 2.0 | 1.9 | 2.8 | 2.5 | 2.4 |
| Triple-glazed, argon filled, low-E (εn = 0.2, hard coat) | 1.9 | 1.6 | 1.5 | 2.3 | 2.0 | 1.9 |
| Triple-glazed, argon filled, low-E (εn = 0.15, hard coat) | 1.8 | 1.5 | 1.4 | 2.3 | 1.9 | 1.8 |
| Triple-glazed, argon filled, low-E (εn = 0.1, soft coat) | 1.8 | 1.5 | 1.4 | 2.2 | 1.9 | 1.8 |
| Triple-glazed, argon filled, low-E (εn = 0.05, soft coat) | 1.7 | 1.4 | 1.3 | 2.2 | 1.8 | 1.7 |
| Windows and doors, single glazed | 4.8 | 5.7 | ||||
| Window with secondary glazing | 2.4 | |||||
| Solid door (exposed) | 3.0 | |||||
| Solid door between house and an unheated space (semi-exposed) | 1.71 | |||||
| Solid door between apartment and an unheated space (semi-exposed) | 1.36 | |||||
| Metal uninsulated garage door | 5.9 | |||||
Notes
| Wood or PVC-U frame | U-value adjustment for roof window (W/m2K) |
|---|---|
| Single glazed | +0.3 |
| Double glazed | +0.2 |
| Triple glazed | +0.2 |
| Metal frames | Adjustment to U-value (W/m2K) | |
|---|---|---|
| Window | Roof window | |
| Metal, no thermal break | +0.3 | +0.7 |
| Metal, thermal break 4 mm | 0 | +0.3 |
| Metal, thermal break 8 mm | -0.1 | +0.2 |
| Metal, thermal break 12 mm | -0.2 | +0.1 |
| Metal, thermal break 20 mm | -0.3 | 0 |
| Metal, thermal break 32 mm | -0.4 | -0.1 |
2. For half-glazed doors (approximately) the U-value of the door is the average of the appropriate window U-value and that of the non-glazed part of the door.
Example: A solid wooden door [U-value of 3.0 W/m2K] half-glazed with double glazing [low-E, hard coat, argon filled, 6 mm gap, U-value of 2.5 W/m2K] has a resultant U-value of 0.5*(3.0+2.5) = 2.75 W/m2K). Source: SAP 2005
3. When the window U-value is declared using certified data rather than from Table 2.28, the metal frame adjustment above is generally accounted for in the certified window U-value. Therefore, when a non-default window U-value is applied, DEAP assumes the metal frame adjustment to be zero.
4. The roof window adjustment applies for all roof windows, regardless of whether default or non-default U-values are used. Where a certified user defined roof window U-value includes adjustment for the roof window (instead of table 2.28 notes 1 or 2), do not select the roof window check box in DEAP. Enter the adjusted certified U-value as well as a certified solar transmittance. Ensure horizontal or north is selected correctly from the orientation dropdown.
5. Selection of correct window orientation is detailed in Table 2.34 footnotes.
| Type of glazing | ID | Total solar energy transmittance (for calculation of solar gains) | Light transmittance (for calculation of lighting requirement) |
|---|---|---|---|
| Single glazed | 1 | 0.85 | 0.90 |
| Double glazed (air or argon filled) | 2 | 0.76 | 0.80 |
| Double glazed (Low-E, hard-coat) | 3 | 0.72 | 0.80 |
| Double glazed (Low-E, soft-coat) | 4 | 0.63 | 0.80 |
| Window with secondary glazing | (2) | 0.76 | 0.80 |
| Triple glazed (air or argon filled) | 5 | 0.68 | 0.70 |
| Triple glazed (Low-E, hard-coat) | 6 | 0.64 | 0.70 |
| Triple glazed (Low-E, soft-coat) | 7 | 0.57 | 0.70 |
Notes
As outlined above, there are different types and notations for solar transmittance. If in any doubt about the solar transmittance value provided in test data, check with the supplier/manufacturer/test laboratory to ensure you use or derive the correct g┴ value.
| Frame type | Proportion of opening that is glazed (FF) |
|---|---|
| Wood | 0.7 |
| Metal | 0.8 |
| Metal, thermal break | 0.8 |
| PVC-U | 0.7 |
Note: If known, the actual frame factor must be used instead of the data in Table 2.32 provided it is obtained either for the standard window configuration defined in BRE 443 or it is an area-weighted average of all windows in the dwelling. Frame factors from certified test data for windows must be used where available.
| Overshading | % of sky blocked by obstacles | ID | Winter solar access factor | Summer solar access factor | Light access factor |
|---|---|---|---|---|---|
| Heavy | > 80% | 4 | 0.3 | 0.5 | 0.5 |
| More than average | > 60% - 80% | 3 | 0.54 | 0.7 | 0.67 |
| Average or unknown | 20% - 60% | 2 | 0.77 | 0.9 | 0.83 |
| Very little | <20% | 1 | 1 | 1 | 1 |
Notes
Overshading of a window is an estimate of the sky that is blocked when viewed outwards from the centre point of the window in question. Objects obscuring the skyline below or behind the window centre point should be ignored. Objects obscuring the skyline may be close to the window, such as balconies and window reveals, or far away from the window, such as landmasses and other buildings.
| Orientation | Month | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
| North | 0.27 | 0.51 | 0.91 | 1.36 | 1.89 | 2.12 | 1.94 | 1.57 | 1.06 | 0.61 | 0.33 | 0.20 |
| NE/NW | 0.27 | 0.53 | 1.02 | 1.68 | 2.34 | 2.49 | 2.28 | 1.92 | 1.29 | 0.69 | 0.33 | 0.20 |
| E/W | 0.44 | 0.88 | 1.51 | 2.24 | 2.88 | 2.90 | 2.68 | 2.44 | 1.87 | 1.18 | 0.56 | 0.37 |
| SE/SW | 0.94 | 1.53 | 2.05 | 2.60 | 3.02 | 2.88 | 2.74 | 2.69 | 2.35 | 1.84 | 1.19 | 0.87 |
| South | 1.22 | 1.93 | 2.37 | 2.66 | 2.86 | 2.67 | 2.59 | 2.66 | 2.56 | 2.23 | 1.55 | 1.15 |
| Horizontal | 0.64 | 1.31 | 2.31 | 3.58 | 4.77 | 4.86 | 4.52 | 3.96 | 2.81 | 1.64 | 0.84 | 0.50 |
Notes
Regarding window orientation:
Source: Calculated from Met Eireann data