What can we do about climate change?

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Constructing buildings is in most cases harmful to the environment. So what can we do as designers to reduce this impact as much as possible (and ideally reverse it)?

 

 

Modern Dulwich house maximises natural light and tree views with full-height corner window

 

Insulation, insulation, insulation!

In the same way as a warm coat or a duvet, insulation is what keeps the heat inside the building in winter and outside in the summer. It is an obvious one to tackle first, as not only less energy is needed to heat the inside up but also it is then kept inside, needing fewer top-ups. In addition, the building will feel comfortable in all areas with an even distribution of heat, avoiding cold corners or draughty seats by the windows.

Read more about insulation here.

A well-insulated building can use as little as 10-20% of one that is not insulated at all, that’s an energy saving of 80-90%. This has a direct effect on the system you need to heat the building. A good measure for this is the amount of primary energy needed per year per square metre of building (kWa/m2). A standard Victorian house might require up to 250kWa/m2 while a low energy house would be around only need 50-80. A PassivHaus standard new build would be below 15 kWa/m2 net.

Put another way, conventional boiler systems are rated around 30-40kW peak load. Air source heat pumps for a similar sized well-insulated building would be rated 6-10kW only.

 

Design for flexibility

Building is a carbon-intensive activity, even if done following all best-practice standards and even if the front-loaded emissions of building materials, energy and wastage ultimately lead to a low-carbon home in the long term.

We are therefore aiming to build only as much as necessary, and as rarely as possible. That means the briefing and concept stages of the project need to be robustly tested for future flexibility, allowing for many changes in use during the building’s life time.

We have seen during the pandemic that working from the kitchen table, the sofa, the bedroom or even the bathroom became a necessity for many. Open-plan spaces have been tested and proved not that useful for concentrated work while family life is going on around. This is where little nooks come in handy, corners where you can lock yourself away for a zoom call or simply a moment of concentration. These spaces can be designed in at the outset and do not need to take up much space. When not used for work these nooks can be used for filing bills, exploring the internet with the family or simply a craft project that doesn’t need tidying away every mealtime.

Phasing:

It is not unusual to have big dreams for a project, but only a small budget. The benefit of looking at the big picture of what might eventually be is that you can already put in provisions for future changes. Specifically that could mean running drain pipes up to a loft that might happen in 5-10 years time, installing beam supports for openings that might allow the addition of an extension at even later stage, or upgrading your heating system to allow for more capacity. These preparation works can be identified in the early design stages if enough time and care is given to developing and testing concept layouts at the outset. In the long term they allow for flexibility and future changes without the need to undo the work done to date.

For phased projects it makes sense to insulate the current area of work to best practice levels and work the way through the building as future phases are implemented.

Changing family needs:

As a family grows or children grow older the needs for different spaces will change. While it is lovely to have direct supervision of toddlers in an open-plan space a group fo teenagers with their friends might want more autonomy. We always encourage our clients to think ahead of what might be, building in flexibility of potential future needs. This also includes the provision of lots of storage for toys, books, game consoles, sports kits, bikes etc etc. If thought through early on, this can avoid having to carry out major building work own the future.

Ventilation

Ventilation plays a major role in a building’s carbon footprint:

Cool air from the outside is usually heated inside and expelled back to the outside. Effectively this makes the building act like a fan heater to the environment.

Heat recovery:

Provided a building is well insulated and draught-sealed, it can make sense to fit a mechanical ventilation system with heat recovery (MVHR). This passes the incoming cold air through a coil where it is heated by the passing extracted air.

Ventilation systems can also filter out pollen or fine particle pollution if required – they also keep mosquitos out in the summer!

Note: An MVHR system will need a summer bypass, otherwise the hot air will get trapped in the building.

Summer cooling:

In order to avoid energy-hungry air-conditioning and cooling systems it is important to think about the natural ventilation flow. Provide a variety of opening windows, not just the large sliding doors, so that some can be left open overnight, drawing in cool air. As heat rises the most effective way to get rid of hot air is to open a roof light above. This needs to be combined with active shading systems if the facades face the sun.

See a selection of our low energy projects here

Tech

The use of smart technology is playing an increasingly important role in our homes.

While love triangles between dishwashers, alarm clocks and TVs flourish, tech can also help inform and control the living environment in the background, saving energy and increasing comfort at the same time.

Smart controls

Smartphone integrated heating controls let you programme temperatures with ease, without the need to press little buttons on an awkward panel. Keeping heating low in areas of infrequent use, controlling the house on a room by room basis. Switching the heating on an hour before you get home. These systems can also talk to fire alarms, security systems, lighting etc etc.

Having said this, a well-insulated building has little need for switching the heating on and off – it can afford to keep the temperature at a constant level as topping up the system works out more efficiently than going through peaks.

Low voltage lighting

Most light fittings are now available in LED versions which last for years without the need of changing the light bulbs. LEDs generate less heat than their incandescent counterparts and consume a fraction of the energy as a result.

Tip: Insist on a high colour rendering LED source and ensure the drivers are fully dimmable.

Renewables

We often consider renewables the icing on the cake: They are ‘active systems’ which provide less value for money (and carbon savings for money) if not used in combination with passive solutions such as insulation or reduction in embodied carbon during construction. Yet, they play a crucial part in bringing us closer to zero carbon targets and reduce the load on the national grid.

Air source heat pumps

ASHP take heat out of the external air and run it through a heat exchanger, effectively the same system as a fridge or an air-conditioning system running in reverse. An ASHP produces approx. 3kW for each kW it consumes, making it an efficient and affordable option as a heat source. As ASHPs run on electricity a simple way to lower the building’s carbon footprint is to switch to a sustainable energy tariff. Ideally, ASHPs are combined with photovoltaics, see more below.

Ideally the heat pump would be mounted directly onto the building facade and feed the heat directly into the building. Sometimes however it is necessary to locate the external unit further away, either because there is not enough space or if noise is an issue. In this case a super-insulated duct is installed below ground connecting the unit with the building.

The noise of a heat pump is relatively low and they are getting quieter every year. The noise level is approx. half-way between a fridge humming and a person speaking. The best is to go and have a look at a neighbour’s installation to get an idea fuirst hand.

We have started placing heat pumps in front gardens – enclosed in an acoustic and visual enclosure – based on the fact that ambient noise level along streets tend to be higher than at the rear where most people spend more time outdoors.

Photovoltaics (PVs/ solar panels)

PV arrays are surprisingly easy to mount on flat or pitched roofs and can generate in the order of 3-10kW peak for a typical house. The output varies hugely on the orientation of the building – a 30˚ south-facing roof is ideal but east/ west pitches or flat roofs are also possible, even facades. These are simply less efficient but often there is little choice when working with an existing building.

Conservation officers often prefer to see PV arrays integrated flush into roofs which adds some complexity, yet it can be made to work.

 

Modern Dulwich house maximises natural light and tree views with full-height corner window