19th December 2017 / posted by John
Passivhaus and Oakwrights – the perfect combination for the perfect home
As promised, below we have the second blog in the series featuring expert advice from Andrew Yeats of Ecoarc
As well as very low heating bills, Passivhaus offers comfort and a healthy indoor environment. Attention to detail in design and construction ensures no draughts or cold spots wherever you are in the house. Heat recovery ventilation uses low power fans to provide ample fresh air day and night, warmed to room temperature by a heat exchanger transferring the heat from the exhaust air from kitchen and bathrooms to the incoming air.
Passive House is a rigorous energy standard; energy performance must be demonstrated through the use of the Passive House energy modelling software, which is specifically designed to model ultra-low energy buildings. This is backed up by air leakage tests and commissioning records of the heat recovery ventilation. The standard requires a predicted heating demand of 15kWh/m².a over the usable floor area, adapted for the local climate (average energy use for UK housing stock is around 200kWh/m².a and new-build ranges from 75-100 kWh/m².a). We have developed the design of the house as a compact plan. This form has minimised the heat loss from the house and enabled gains to be received from its share of winter and summer sunshine. Planning design shows that the house can achieve the certified Passive House standard. The insulation levels needed to do this can be met with timber frame wall construction combined with triple glazed windows and airtightness provided by internal boarding and the concealed roof vapour control layer.
The Passive House standard requires an airtightness of 0.6 ach (air changes per hour) @ 50Pa (current Building Regulations require 10.0 ach @ 50Pa). This high standard ensures draught-free comfort, protects the building fabric from condensation due to leakage of humid air, and ensures that the efficiency of the heat recovery ventilation is not bypassed by leakage ventilation. Although this is less than a tenth of the requirement for new UK dwellings, we are familiar with the design requirements of the standard and on other projects have already achieved airtightness of 0.2 ach @ 50Pa in new-build.
Our in-house architectural design team can advise you and evolve your ideas for an Oakwrights Passivhaus design. Our team can also work with your architect and third-party construction experts to develop your Passive House with the added beauty of an oak frame, with our standard Encapsulation (wall insulation) system already meeting the basic Passive House standard.
We will be at the ‘Build It Live’ show in Kent on 3rd & 4th February where our team will be happy to answer any questions you may have about your Passive House requirements - we look forward to seeing you there!