While the low environmental impact of using wood in construction is well known, is a timber frame home energy efficient? For most people planning a new build, limiting damage to the environment during and after construction is a key concern. As a result, the use of timber as a sustainable building material makes it an attractive choice. Modern certification, responsible forest management and replanting methods have all helped to improve sustainable timber construction. Even after transport, the high levels of embedded carbon in oak timber makes it a carbon neutral material. Also, as a natural material it needs no manufacturing or processing that could lead to pollution and energy consumption. However, construction itself is only one part of the energy saving process.
All homes require power and heating of some sort, whether from solid fuels, gas, oil or electricity. Burning fossil fuels in the home or in power stations will produce CO2 and other potentially polluting by products. Fossil fuels are also in ever decreasing supply and needless consumption causes further damage to the planet. In addition, building regulations for new builds are becoming far stricter regarding CO2 emissions. Energy efficient timber frame homes can limit fuel consumption, domestic CO2 emissions and running costs in four key ways:
Timber frame thermal performance
Thermal mass is the ability of a material to absorb, store and release heat. Oak has a low thermal mass, so unlike a brick or masonry structure an oak one would not effectively retain heat. This means that during the winter it would not store heat from the sun and release it during the night. This is one of the great advantages of high thermal mass construction materials. However, during the daytime in winter any stored heat will radiate out to the cooler air outside. As a result, any heat within the house will be absorbed by the building structure itself before warming the interior. This is why it is necessary to set the heating to come on several hours before the occupants leave their beds. Obviously, this is highly inefficient as energy is wasted heating the structure rather than the air inside.
In timber framed buildings, the low thermal mass of the frame reduces the amount of heat absorbed dramatically. The house will warm up in a much shorter space of time and stay warm for longer. There will also be no need to continually heat the house as the heat will not escape through the walls. In summertime, this has the opposite effect of keeping the house cooler as the structure will not transfer heat from outside into the house. This reduces the need for air conditioning or fans, both of which increase energy consumption.
Oak framed buildings are very easy to insulate once the frame is erected. Even with an outer wall added, the gaps between beams are easily accessed. These can be filled with an insulating material and a membrane and inner stud wall attached over them. This is usually achieved with synthetic foam boards, cut to shape and edged with perimeter trims. These provide a waterproof seal between the foam and frame. It can be difficult to fit these completely flush to avoid any heat loss. In recent years, many builders have moved to using wools, natural fibres or glass fibres instead. As these have a soft, springy texture that can be cut slightly larger than the cavity, compressed and pushed into place. They will then expand and completely fill the void with no air gaps. This saves much time and effort for a more effective fit. Wood fibre wools have become very popular due to their high density and similar thermal performance to the frame itself. They are also naturally water resistant, doing away with the need for vapour barriers. It is much easier to effectively insulate a timber frame than a masonry cavity wall. Reflective breather membranes can also be incorporated to block infrared radiation, further aiding heat retention.
Most modern timber framed homes are constructed from green oak building kits. These are designed using increasingly sophisticated software. Advances in design technology and computer aided manufacture have improved the quality of these kits immeasurably. High specification joints and precise measurements give an extremely airtight structure. This level of accuracy can be difficult to achieve when building block by block. Obviously, the thermal efficiency and insulation will be compromised if air can leak through the structure. Heat will escape and more energy will be consumed fighting this. Due to the precision of these kits, it is vital that the foundations for a timber framed house are perfect. If these are not completely level and stable, all the good work of the design will be undone.
While oak framed buildings cannot structurally benefit from solar gain (additional heat from the sun), this can be addressed during design. Incorporating double glazed windows at points where the maximum sunlight falls can exploit its heat. This can be combined with high thermal mass surfaces inside, for example internal stone walls. Local climate and how it will affect energy consumption should also be considered. Orientation of the structure is also important to receive as much sunlight as possible. Any landscape features or other buildings that could overshadow the house should be considered. In addition to heat gains, the extra sunlight will minimise the amount of internal lighting used. Again, this could significantly lower the amount of energy used over time.
Hardwoods Group are experts in the design and manufacture of oak framed buildings. In addition to a wide range of pre designed oak frame kits, we also offer a bespoke design service. Our computer aided 6 axis CNC machine is capable of machining oak timber to precise specifications, whatever the design. Contact us to discuss your requirements, we will be happy to help.