Eco January 2016
How to build a low energy building like this one Conker Conservation, developer Camber Consulting, and materials supplier Ecomerchant have all played their part in delivering a genuinely low energy building at a very affordable price.
The design team at Conker worked with the client bringing with them a raft of proven systems and methodology and an inclusive interconnected approach to delivery, in this case study Paul Mallion a Certified Passivhaus Designer at Conker explains how this was all brought together. Conker have been designing low energy buildings since 1999, this is our approach, demonstrated in the photos: Use the free energy available from the sun; passive solar design has been understood for centuries but still new houses are built that make no concession to orientation. BRE guidance from 1971*describes how good orientation can save 10% of the energy consumption in a dwelling, at zero cost. However, don’t forget to consider solar shading and don’t over-glaze, especially on the east and west sides.
Build to the lowest U values possible, aim for at least 0.15W/m2K for all elements, never use building regulation values as a default. Do not rely on manufacturers for your U value calculations, learn to do them yourself, or use our Android app, ‘Wallnuts’. Calculate for thermal bridges such as cavity ties and fixings, and factor in a workmanship value if using ridged insulation boards, as they rarely get fitted really well.
You will need to work with a knowledgeable materials supplier, it is essential to have a secure supply chain this is why we make sure our supply partners are part of the construction process right from the start in this case Ecomerchant, This is particularly true of insulation so you know what is available and the insulation properties, rather than rely on a single type of foamed board for all purposes. Dense insulations like woodfibre are better at limiting heat gain in summer. Compressible insulations like wool are better in between timbers which may shrink over time. Breathable insulations are essential for work on historic buildings. ‘Build tight - ventilate right’ is a phrase decades old, but still true. Make the building airtight, and carry out an air leakage test before completion. Aim for a figure of 1.0m3/m2hr or 1.0 air changes an hour. Don’t confuse draughts with ventilation. Become familiar with airtight membranes and tapes and how to use them. Never rely on builders foam or mastic for airtightness, these will shrink and fail within a few years. Very airtight buildings will need a mechanical ventilation system, which will provide consistent air quality, whereas natural ventilation will constantly vary and rarely be right. Heat recovery ventilation is worth the
*BRE Information Paper ‘Site layout for sunlight and solar gain
investment when properly designed and installed, but cheap systems are a waste of money. Make triple glazing your default. Costs have tumbled over the last 10 years, and a wide range of options exist. Timber frames or thermally broken frames are best. The improved thermal comfort and noise attenuation is well worth the investment. Triple glazed windows can be icy on the outside, but still warm to the touch inside. Install them using airtight tapes or compression seals, and low expansion window foam which remains pliant and will not shrink. Consider building to the AECB Carbonlite Silver Standard or the Passivhaus Standard, to prove how well your building performs. Enjoy a comfortable low energy building with good air quality.
Design and Project Management Conker Conservation Ltd 01227 786900 www.conker.cc Materials Supply Ecomerchant www.ecomerchant.co.uk 01793 847 444 Developer Camber Consulting www.camberconsulting.me