Although not self build, the two passivhauses at Ebbw Vale may be very relevant to many self builders. Built in 2010 as show houses mainly for the attention of housing associations, they are attractive and innovative while being relatively modest. The 3 bed Larch House is clad with a locally sourced larch rain screenthis is a (usually thin) outer cladding on a wall which prevents rain, snow, etc getting at the structure of the wall behind. see more on rain screen and Lime House has a natural lime render.
Considerable effort has been put into using local materials where possible and also enabling local businesses to learn the new techniques required for services, timber frame manufacturing and window/door production etc.
Larch House not only achieves the PassivhausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. standard but is also zero carbonbit of a slippery fish. It tends to mean that a building uses no carbon (oil, coal, etc) to heat it (meaning in a 'net' way). It usually ignores the carbon which goes into building it (the embodied energy). See the page on Zero Carbon? due to the large areas of solar collectors on the roofs. This achieves CSHCode for Sustainable Homes. A delightful tool for assessing how green a home is. Unfortunately now withdrawn (2015) by this short sighted government. Level 6, a UK first. Lime House achieves CSH level 5
The south elevation of Larch House has more than 50% of its surface glazed with certified triple glazed windows to catch winter sun. Louvre blinds are fitted to prevent overheating in summer. The main construction is 225mm glass wool insulated closed timber frame with extra wood fibre insulation board on the outside. The external walls total about 450mm thick with a U-value of 0.1W/m²K. The air tightnessA measure of how leaky a building is to air. In other words, how draughty it might be. There are now standard fan pressure tests to check how air tight a house is and the Building Regulations have minimum standards for all new houses (L1A – Conservation of fuel and power in new dwellings (England)). A much higher degree of air tightness is covered by the Passivhaus standard test achieved a remarkable 0.2 ac/h @n50
The other elevations have low levels of glazing.
A slightly different approach was taken here. The UK climate (and particularly the somewhat higher altitude of this location) tends to be more overcast than in mainland Europe where the Passivhaus standard is most often applied and south facing passive solar gain is relatively less important so glazing was not used to the same extent as the Larch House: rather the heating relies more on internal heat gains and higher insulation values
The space given over to the MVHRMechanical Ventilation with Heat Recovery. This is usually a double fan arrangement which extracts stale air from the house and sucks in fresh air at the same time. As the warm stale air is blown out, heat is extracted from it and passed over to the cool incoming air by means of a heat exchanger. With the latest technology, over 90% of the heat can be recovered. (see Passivhaus standard) is quite considerable. Both houses used one of the most efficient heat exchangers available. The Paul unit is rated at over 92% efficient. This is the grey box in the picture with the heavily insulated black ducting. The silver unit is the heater for the incoming air after it has been through the heat exchanger. Note also on the left the orange pipework for the fire sprinkler system which is becoming mandatory for all new housing in Wales.
United Wesh Housing Association – technical information.
bere:architects – Lime House – general information
bere:architects – Larch House – general information
AJ article – general info.