Making our homes more energy efficient is a priority for many, but it’s important to think about the full picture to avoid any unintended consequences, and ensure your improvements work as intended. Architect Gearóid Carvill shares some of the main things to consider.
With our concerns about cost and climate, it has never been more important to improve our homes’ energy efficiency. When planning your project, it is important to think holistically to avoid unintended consequences and ensure that improvements perform as designed for you, your family’s and the wider societal benefits.
Beware of hot air
Insulating to reduce heat loss, or the “fabric first” approach, is the best way to begin your energy efficiency plan. Where possible, it is important to “join the dots”, so, for example, new floor insulation connects with wall insulation and attic insulation with wall. Care should be taken at windows as wall insulation needs to connect to your windows at the window reveal. Areas of uninsulated wall become cold bridges and the rate of heat loss increases through these gaps.
Insulation upgrades need to be considered with ventilation because the warmer we make our homes, the greater carry capacity our internal air has for moisture and some systems, particularly dry lining, can result in cold bridging. When this warm air meets a cold surface, moisture condenses and over time can result in mould, which is hard to get rid of. Insulation upgrades invariably make our home more airtight, which is a good thing, but apart from excess moisture there are also pollutants such as volatile organic compounds (VOCs) from furniture and paint, as well as off-gassing from cleaning products that it is important to vent out. Bottom line, it is crucial to ensure ventilation meets building regulation requirements and this extends beyond our bedrooms and living rooms to any space you don’t want to find mould or rot in.
Choose insulation carefully
We have a rich history of construction in Ireland and there are many types of wall construction and now a variety of insulation materials to choose from, but they don’t all work together. Your geographical location in Ireland (and importantly, your exposure to rain) as well as the type of construction: solid, cavity, or block, will determine which system will work best for you. Wall insulation is not always appropriate either, as it may cover up or result in the loss of decorative features important to the character of the home.
Window peak
We’re obsessed with light but in a super-insulated home, excessive glazing can result in overheating. It’s a new phenomenon, but one that is likely here to stay so altering homes to provide walls of glass needs to be considered in terms of balancing comfort with aesthetics. It is important to consider a window’s thermal performance and different windows will have different thermal specifications (U-values), which is the rate of heat transfer. The lower the figure, the better the insulator. The effect of glazing on internal temperature can be calculated by designers using the Passive House Planning Package, amongst other software solutions.
Not all taps need to be high pressure apart from the kitchen sink and it’s inexpensive to retrofit as you don’t need to replace the tap. Kitchen and bathroom suppliers should be able to tell you the flow rates for the appliances they are selling you.
The time to ventilate
As well as the traditional hole in the wall vents and trickle vents that come preinstalled in modern windows and doors, there are some more sophisticated and efficient solutions to providing clean air to your home. The problem with these traditional solutions is that you need to remember to open and close them. Demand controlled ventilation (DCV) use vents that open when they detect humidity and separately have fans to extract air from bathrooms and utility spaces. So, when your home is unoccupied, there’s no heat being lost.
Mechanical ventilation with heat recovery (MVHR) is a where the heat from stale air is transferred to the incoming fresh air, preheating it, and the incoming air can also be filtered for dust and pollen. It’s typically a fully ducted system with pipes to every room so can sometimes be tricky to install in retrofit, though there are some simpler recovery systems available, such as the Lunos system which uses individual wall-mounted fans installed in pairs, which alternate between air intake and extraction.
Energy down the drain
As our homes become more heavily insulated so it will become apparent that hot water production uses a lot of energy. The Building Energy Ratings were revised a few years ago and water use is now calculated as part of your home’s BER by the number and flow rate of taps and appliances.
Reducing demand through small adjustments to existing taps and recovering heat from showers and baths can be hugely impactful. Not all taps need to be high pressure apart from the kitchen sink and it’s inexpensive to retrofit as you don’t need to replace the tap. Kitchen and bathroom suppliers should be able to tell you the flow rates for the appliances they are selling you. Recovering heat from wastewater should also be considered as part of any refurbishment project, which works by taking the heat from water flowing down the drains to preheat incoming mains water.
You can’t manage what you can’t measure
Knowing your home’s BER is an important start to any project which aims to increase its energy efficiency. But does your house perform to the level of its BER or is there a performance gap? A simple way to answer this is to keep a note over a year of your bills and see how many units of gas and electricity you are using per year. Your BER gives an estimate of the energy needed to light, heat and provide hot water. It does not estimate appliance use but can be estimated at 3-4,000 kW per year.
This type of evaluation needs to be undertaken for at least 12 months, in particular with heat pumps as their rated efficiency includes the summer use (they are less efficient in winter). If you can’t answer these questions, it’s worth asking an expert or sustainability will always be a mystery as will your fuel bills! Post-occupancy evaluation is a term used to describe this review, which can be agreed as an additional service with your designer or architect.
Maintaining control
Heating controls are crucial for energy efficiency and comfort. A modern thermostat should offer time, temperature and zone control. Your system should also be zoned, typically with bedrooms in one zone or temperature setting and living spaces in a separate zone. This way, you don’t have to heat your bedroom when you are really looking for warmth in your living room, and your boiler switches off when the set point temperature is reached. None of these settings feature in a traditional boiler clock, so boilers keep running regardless of internal and external temperature.
Grant aided
The cost-of-living crisis has included significant inflation in construction costs. The Sustainable Energy Authority of Ireland (SEAI) grants play a role in tempering these costs. Perhaps more significantly, the SEAI maintains databases of registered contractors and conducts random checks on site. This helps ensure standards on site meet relevant building regulations standards as contractors can be penalised for mistakes and/or potentially de-listed from the register. Manufacturers of individual heating systems also keep registers or lists of contractors who have received training for that brand. Using one of these contractors can sometimes provide an extended warranty for your new boiler
or heat pump.
Embodied energy, the new frontier
The energy we use to heat and light our homes is sometimes referred to as operational energy. The energy that is used to make the materials used in their construction is referred to as embodied energy. Our current standard of construction is energy and carbon intense. Concrete blocks, steel, glass, aluminium and even some types of insulation require significant amounts of energy and water to be produced.
The energy required to make the materials for 1m2 of new build construction or home extension is estimated to currently produce 1,400kg CO2, the equivalent of burning 600 litres of crude oil. It’s why existing buildings are such a valuable resource, and our built heritage is not only of huge cultural value but also an environmental one. So, no matter how energy efficient your home extension or refurbishment might be, it might never in your lifetime save the energy that was lost in making it! Simple changes in specification can reduce this figure so it’s worth asking the question of your designer.
Maintain, reuse, recycle
It’s tragic in this context to see skips filled with material from home refurbishments that could have been reused elsewhere. Kitchen cabinets, bathroom suites, floorboards, joists, tiles, bricks, windows can all be reused intact. They can also be sold on for cash or at least given away on DoneDeal or equivalent. Some contractors might charge you extra to carefully dismantle rather than smash to bits, but with a little planning, it is possible to reduce a lot of landfill through sale or freecycle.
Recently, the Irish Green Building Council had set up a construction materials exchange scheme where new unused materials can be collected in an online database so they can be identified for reuse elsewhere. Currently, it is normal practice that these materials are skipped on site. Some studies have suggested that as much as 30 per cent of the materials that are delivered to a job end up in landfill. It’s a crazy amount of waste.
It can be daunting, confusing and frustrating keeping up with new technology, systems and building standards. However, the overriding principle is simple: it’s about conservation, of energy, of materials and our environment.
Illustration: Tara O’Brien
This feature originally appeared in the autumn/winter 2023 issue of IMAGE Interiors. Have you thought about becoming a subscriber? Find out more, and sign up here.
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