Year Round Comfort for Your Renovation or New Build

Hardly anyone comes to us asking for a “sustainable home”. They might mention ecological materials, or a heat pump, but give it a few minutes and we soon move on to comfort – being warm enough in winter, and not baking in summer.

Fortunately, the changes that make a home comfortable are pretty much the same ones that reduce its energy use.

But the timing of decisions matters a whole lot more than you might think. A good decision made early in the design can cost next to nothing, while delaying the same decision can add more cost than is necessary….or, potentially, be impossible. For each idea we’ve given you a quick guide:

Cost goes from £ to £££, compared with the other ideas we’re suggesting (this isn’t a quote!)

Comfort is how much difference you’ll likely feel, from no hearts to three

Decide by is when you need to have made your mind up. Concept means the early design stage, before the planning application is submitted. Technical design is the detailed set of drawings a builder prices from.

🍒 The cherry on top is the lovely to have items, the things to include once everything else is in place.

Start with the whole house, even if you can’t do it all at once

£ | Concept

Once we have this information, we put together an improvement strategy. When possible we don’t suggest replacing things that aren’t ready for replacement – why waste perfectly good windows or a relatively new boiler, when they might still have another 5 or 10 years of good service left! The plan is also not to have to unpick work you do now when you come to doing work in the future. It also helps stop someone fitting a heat pump to a house that isn’t yet ready.

Lots of people can’t – or simply don’t want to – do everything in one go, and that’s absolutely fine, as long as every stage is properly considered and is heading for the same goal.

Quick draught-proofing

£ | | Any time

If your whole house plan is going to take a few years, sealing the obvious gaps now makes a real difference for very little money. Think around old windows and doors, between floorboards, the loft hatch and any unused chimneys. Just make sure each room still has a way to get fresh air, so you don’t swap draughts for damp. It’s no substitute for proper airtightness later, but the short term benefit will be worth it.

Picking a standard to work to

A recognised standard gives you a clear target, and the quality assurance of checking that what was designed is what was actually built – if you choose to have the work certified. We’ve talked through the principles behind these in How Can Passivhaus Principles Improve Your Renovation? so here’s just the short version of how they differ.

Passivhaus

£££ | | Concept

The full works, and really only realistic for a new build. There are many considerations, such as the shape of the house, which way it faces and the size of the windows, shading and mechanical ventilation requirements. These all need full consideration from the very first sketch. Passivhaus should be a conversation from day one.

EnerPHit

£££ | | Concept

This is Passivhaus for existing buildings – a whole house retrofit that could be phased. It’s brilliant, and it’s tough. Some houses just can’t get there no matter how much insulation and airtightness tape is used, because their shape, orientation or physical constraints work against them.

AECB CarbonLite Retrofit

££-£££ | | Concept

This is the one I find myself recommending most often. I’m a Certified Passivhaus Designer and an approved AECB Certifier, so I’m very attached to both…. It uses the same modelling and the same thinking as Passivhaus, but is more forgiving.

An AECB home is allowed roughly twice the heating energy demand of an EnerPHit one. I don’t think most people would feel the physical difference, except maybe on the very coldest days of the year. It’s also cheaper to certify. Moisture in existing houses is taken very seriously, and you can do it in steps.

On one AECB CarbonLite retrofit we designed for a semi-detached house. Wrapping the house in insulation, alongside a small extension and loft conversion, was modelled to cut the heating demand by 70%. That’s a big difference to how a house feels in the long, chilly winter months.

The fabric: walls, windows and air

Whichever standard you go for (or none at all), this is where comfort really comes from.

Insulating the walls

££-£££ | | Concept

If one thing changes how a room feels, it’s warm walls. You no longer need to worry about mould growing behind the sofa or wardrobe.

Insulation can be applied either outside or inside.

Outside usually performs better, but it changes the look of your house and may need planning permission, so it needs to be decided early. Inside costs you a little floor space and will disturb anything fixed to the wall.

Both need a lot of care at junctions, because that’s where cold bridges happen. And no one likes a sneaky cold bridge.

Natural, vapour open materials

££-£££ | | Technical design

Older houses with solid walls (most brick buildings built before the 1930s) were designed to get damp and dry out again. The house was draughty enough via leaky floor boards, the chimney flue and single glazed windows to carry moisture away. Line them with the wrong insulation and the moisture gets trapped with nowhere to go, and that’s when rot and mould set in.

Applying materials such as wood fibre, hemp, cork and lime lets those walls carry on ‘breathing’. By ‘breathing’ I mean allowing vapour to move inwards and outwards through the wall. They’re kinder to the planet as well, and I love working with them. In an old house they’re often the safest choice, not only the greenest.

Windows

££ | | Technical design

Old windows are the weak point for chill, especially if they’re single glazed, and they’re often the source of that mystery draught. Wherever you have big areas of glass, or a favourite chair right next to a window, we always recommend triple glazing. You really do feel it. Your cat will appreciate the cosy spot too.

Draughts and fresh air

££ | | Concept

Seal up a leaky house properly and the draughts disappear, which usually makes a very noticeable difference to your comfort. But a well-sealed house needs fresh air brought in on purpose, and that’s the job of MVHR (mechanical ventilation with heat recovery). It draws stale air out of the kitchen and bathrooms, brings filtered fresh air in, passing the warmth from one to the other on the way.

You end up with much less dust and no draughts. In a whole-house project we think it’s always worth it. Remember that even if you have MVHR, you can still open the windows – in both summer and winter!

There is one big catch though, the system needs ducts routed through the house, and those have to be planned early in the project. It could be left until the technical drawings, but we feel the feasibility and impact of routing ducts in and around existing structure is better to know sooner rather than later so that if there is an issue it can be planned for.

Keeping cool in summer

£ | | Concept

A well insulated house holds onto its heat beautifully, which is exactly what you want in winter. In summer, not so much! Big south or west facing windows with nothing to shade them can turn a lovely new room into a greenhouse.

The good news is that the fix is mostly down to design, so if it’s thought about early, it can be mitigated against. Getting the window sizes right does help, and so do deep window reveals, roof overhangs, solar control glass, external blinds and tree planting. On that AECB semi we added a little pergola over the south facing patio doors for plants to scramble across. Choose a fragrant climber that loses its leaves in autumn and you get shade, and fragrance, in summer, with the low winter sun still finding its way in for a bit of winter warmth.

Being able to open windows on opposite sides of the house makes a big difference in cooling the house at night after a hot day. And if you have MVHR, a summer bypass stops it warming up the fresh air on its way in.

Heating comes after the fabric

Air source heat pumps

££ | | Technical design

Heat pumps are great in a well insulated house and a costly mistake in a leaky one. Most of the horror stories you’ve probably read are about heat pumps fitted to leaky houses! So, choose fabric first please.

If your boiler is still fairly new, then leave it be. Plan for the heat pump now, with space for a hot water cylinder, and radiators or underfloor heating sized to run at lower temperatures, then make the switch when the boiler finally gives up. There’s no point replacing something that isn’t broken.

Ground source heat pumps

£££ | | Concept

More efficient again, and almost silent. You’ll need a fair bit of garden for the pipes (or a borehole), though, so it’s an early decision and a bigger spend. It’s worth it if you have the space.

Smart heating controls

£ | | Technical design

Clever thermostats and room by room controls get a lot of attention, and they are handy. In a leaky house they help you heat only the rooms you’re using. In a well insulated one they have far less to do, because the temperature hardly moves! Nice to have, but not where the comfort comes from.

The cherry on top 🍒

Solar panels and batteries

££ | | Can be added later

Let’s be honest, solar panels won’t make your home feel one bit warmer. That’s why I call them the cherry on top. Once insulation, windows and air are sorted they’ll take a good chunk off whatever’s left of your bills, and if the budget is stretched now, they can be added later.

A battery lets you keep what you generate during the day for the evening. You can also charge the battery up overnight on a cheaper tariff.

From 24 March 2027, new homes in England will need solar panels and low carbon heating built in. So, on a new build they’re part of the cake rather than the cherry.