SAP2012 was unveiled under a cloak of darkness and without fanfare at the start of June. Until Part L is confirmed and released in England and Wales (and the updated Section 6 in Scotland), the SAP methodology will not be used, so we’ve got a few months to understand what’s changed, and how that may impact next year’s building projects.
Over this series of blogs, we’ll look at SAP2012 in detail:
The last time Part L was updated in 2010, party walls were introduced for the first time as a potential area of heat loss for a dwelling. Ever since this release there has been confusion, particularly within blocks of flats and complexes, about how different types of internal wall should be treated in the SAP.
This new methodology gives better definitions about the differences between party walls, and the expected heat losses from them.
For a conventional row of houses or small block of flats, the definition is quite straightforward. A party wall is any wall between the dwelling in question and another heated space. This would include another dwelling, a heated commercial unit, a corridor or stairwell in a block of flats (which has its own heating system) or a heated communal area.
In these cases, party walls are seen to have no heat loss if they’re completely solid, structurally insulated panels (SIPS) or fully filled and sealed cavity walls. (They should be sealed at the top and bottom of the building as well as vertically).
Uninsulated walls will not meet building regulations
If a party wall is not insulated but suitably sealed, the assumed U-Value is 0.20. An uninsulated and unsealed cavity party wall will not meet Building Regulations as the heat loss is deemed to be too high.
If a party wall adjoins an unheated staircase, communal area or commercial unit, it is treated as a heat loss wall and needs to be insulated to a similar level as the external walls.
For larger buildings which have a mix of residential and commercial units, the definition of party walls becomes more awkward. If the wall is between a dwelling and another dwelling or an area which is heated in the morning and evenings only, then it’s counted as a party wall.
If the adjoining space is heated, but during the day only (such as an office), it’s treated as an external wall, but the U-Value is halved to take into account the heat gain during the day.
If the adjoining space is unheated, heated to a low level or heated only intermittently, it’s considered to have the same amount of heat loss as an external wall, and should be insulated accordingly.
The next blog will look at the changes to Waste Water Heat Recovery systems... For daily updates on the changes to SAP and Part L 2013 follow us on Twitter @EnergistUK