Sustainability and energy reduction measures in your new home or residential extension
It is unsurprising that in these times of rising energy costs and environmental issues our design team at Ecclesall Design is sometimes asked how we incorporate sustainability and energy reduction elements into our architectural designs.
Sustainability and energy reduction in new build houses
There is an easy answer when we’re designing a new build house from scratch – at a minimum, we ensure compliance with Building Regulations standards which cover all aspects of construction, including foundations, damp proofing, the overall stability of the building, insulation, ventilation, heating, fire protection and means of escape in case of fire.
For those who are interested in achieving for their new home more energy efficiency than the minimum standards required by Building Regulations, you may have heard of passive house design, which offers an approach for further reducing energy demand and CO2 emissions via:
· No thermal bridging
· Superior windows
· Mechanical ventilation with heat recover
· Quality insulation
· Airtight construction
In conjunction with independent energy consultants, Ecclesall Design can offer the Passivhaus Planning Package (PHPP), a design tool produced by the Passivhaus Institute. We should mention that there is a premium to be paid for this service due to the complexity and additional time involved in ensuring that every element of the architectural design has been thoroughly evaluated, and we need to be advised at the initial briefing stage that Passivhaus standards would be required. Compared to benchmark data for UK Building Regulations standard dwellings, the uplift in building costs for a Passivhaus residential property is calculated to be around 20-25%. However, a recent study shows that whole life costs of houses built to Passivhaus standards can be 2-5% lower than traditional construction methods, even accounting for the higher build costs.
The higher construction costs mean that in our experience, most prospective new house developers who self-build or intend to sell upon completion initially express an interest in passive house technology. However, they generally decide that complying with Building Regulation standards will be sufficient due to these increased costs.
Sustainability and energy reduction in house extensions
All our extensions are designed to meet current Building Regulations. If you were to wish to upgrade any elements within your home – either to the new extension or to the existing house – to a higher specification than that required by Building Regulations, this would not be a problem. It would be for the builder to install, for example, additional thickness of insulation. In extensions with large amounts of glazing, a homeowner might choose to upgrade to thermally insulating glass (also known as low-emissivity or low-E glass); this usually forms the inner pane of an Insulating Glass Unit (IGU). Thermally insulating glass has a transparent metallic coating that reflects heat from radiators or fires back into the room rather than allowing it to escape through the windows. It controls solar gain and maximises natural light. There are several manufacturers in the UK that supply this product.
If your new extension has what is described as ‘excess glazing’, SAP or thermal calculations will be required by Building Control. These calculations will show that an increase in insulation somewhere within the home will be required to compensate for the loss of heat through the excess glazing. This can include thermal glass or an upgrade to the existing roof insulation, new glazing to windows or doors in the existing house or a new boiler. For an extension not to require excess glazing calculations, it is allowed to have 25% of glazing to floor area and the area of any existing openings that are being covered or removed as part of the extension work.
Upgrading the insulation and thermal properties in your house
As regards ‘ retrofits’ in domestic properties (ie fitting new products to existing buildings), as can be seen from the following table reproduced by Ecclesall Design from BEIS (UK Government Department for Business, Energy & Industrial Strategy) Research Paper 2021/014, there is no one solution that stands out beyond all others. Some such as loft insulation are relatively easy and inexpensive to introduce, replacement windows and doors are often desired from an aesthetic point of view anyway, and the increase in thermal performance is then a nice bonus. Others, such as cavity wall insulation, are not particularly cheap and have a chequered history with problems such as damp ingress. The feasibility of retrofitted suspended timber ground floor insulation depends on whether there is a cavity such a cellar beneath the floorboards that makes access easy, or if the homeowner is willing to have existing floorboards lifted and replaced with new flooring once the insulation is in place.
Our experience is that clients tend to go for retrofit options that are easy to accomplish whilst the building work is taking place, so perhaps additional loft insulation, new doors/windows and maybe insulated plasterboard on external walls, although these would reduce the room size by around 60mm per each wall insulated, and insulation beneath the ground floor floorboards if access is available.
If a homeowner is particularly keen to engage with a formal modelling process to inform their energy efficiency measures, we would be able to introduce a third party consultancy service that offers a design review for £500 + VAT. The design review usually involves a 2-hour meeting via Microsoft Teams or Zoom. The consultants would study the project plans, images and key questions in advance. Ecclesall Design would be willing to attend the meeting free of charge if you were interested in this. We would then suggest amendments to the drawings and other specifications as part of our service.
The meeting would consist of:
· Objectives of the newbuild/retrofit project and priorities
· Overall building design/retrofit plans
· Options for materials, products & services
· Risks around moisture
· Cost and buildability
We hope you have found this blog interesting and helpful. We have described above certain measures, such as increasing the amount of loft insulation that are ‘quick wins’ for anyone wishing to reduce their heating bills, improve comfort, and generally contribute to a reduction in heat loss to the environment. Still, care needs to be exercised as not every solution touted in the media is cost-effective or practical. The subject of gas-fired boilers v ground source heat pumps is a topic best discussed with an expert in the field – we are very happy to show the location of heating units on our drawings following input from specialists and after instruction from our clients.
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