I’m planning a planning-exempt rear extension of about 40sq m to my semidetached home. I’ve been told that if the extension increases the house’s overall surface area by more than 25 per cent, I may need to upgrade the energy rating to at least B2. I’m confused about what this requirement actually means in practice. What kind of upgrades might be needed, and what sort of extra cost could this involve?
First, it is important to note that even where an extension project is exempt from planning permission, it must still comply with building regulations, and this is where the 25 per cent rule comes in.
The rule states: “Where more than 25 per cent of the surface area of the existing dwelling [this includes the walls and the roof] is being renovated, the energy performance of the building or the renovated part of the building must meet the new energy efficiency requirements [Ber of B2 or equivalent]. The standards must be met if it is technically, functionally and economically possible.”
Taking a typical three-bed semidetached house as an example, you may not reach 25 per cent of the surface area based on the fact you are limited to extending to the rear only, to comply with the planning exemption. Additionally, there are no definitive guidelines on what constitutes “technically, functionally and economically possible”, and this will need to be assessed on an individual basis.
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Notwithstanding these points, it is certainly in your interest to improve the energy efficiency of your home and it is important to know where you’re starting from. Get a Ber report carried out for your existing house as this will inform your architect on how much or how little intervention is needed to achieve a higher rating.
Your architect and quantity surveyor can confirm if the rule applies to your exact project and provide a shopping list of options to improve the performance of your house, taking into consideration the feasibility of implementing the measures.
Typical measures include:
- Insulation upgrades: Pumped cavity, external wall and attic/roof insulation upgrades or internal dry lining.
- Window and door replacement: Replacing existing with high-performance double- or triple-glazed units.
- Heating system upgrades: Replacing oil or gas boilers with a heat pump, though this generally requires good insulation levels to perform efficiently.
- Airtightness and ventilation: Improving airtightness combined with appropriate ventilation measures to prevent damp and condensation.
- Renewables: Solar PV panels.
Some of these options are simpler to put into practice than others and your home’s position on the Ber scale will dictate how many are required to achieve a higher target rating.
How much might it cost? The costs will vary depending on factors such as property size, type, current Ber and the condition of the house, so it would not be appropriate to provide a cost estimate. However, there are several grants available through the Sustainable Energy Authority of Ireland that help with the viability of upgrades.
While the cost is important, it’s also crucial to consider the long-term value of the upgrade measures with regard to current and future energy costs.
Moving forward, as your plan is to avail of the 40sq m planning exemption, I recommend monitoring the Government’s proposed changes to planning exemptions for domestic dwellings, which is being dominated presently by the modular garden unit discussion.
The plans, which are already drafted, include adjustments to the design constraints associated with the current 40sq m exemption and additional exemptions such as attic conversions and energy/retrofit works.
Lastly, engaging with qualified professionals early will allow them to give you all the information needed to make informed decisions at an early stage, so you know the scale and cost of project you are committing to.
Craig Potter is a chartered quantity surveyor and a member of the Society of Chartered Surveyors Ireland
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