Planet friendly architecture, guidance and inspiration​
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Taking the fuss out of architecture and building projects

Sustainability considerations when planning an extension to an old building

When extending a building how much of the old building should you demolish? Do you actually need an extension in the first place?

What are the current standards for the new building work? How can I meet those standards?

What about the old building that you are going to add an extension onto? Will it be as comfortable or perform the same as the new bit of building?

It can be a bit of minefield with all the conflicting opinions and information out there. So, what’s the best thing to do? Well, now, read on to find out my opinion on all of this stuff. A practical and sensible approach is needed, suited to your individual circumstances.

Extensions + sustainability - demolition, the extension + the existing host building

Demolition

Generally, new building work uses up more energy and emits more carbon than retaining an existing building, altering, upgrading and retrofitting the old building.

Do you actually need an extension? If your building is already quite big, can you just alter or remodel your existing building without extending at all? Simply remove a few walls and change the layout?

Often by thinking outside of the box [or rather, her-hum, inside the existing box] and by flipping things around where not considered before, you might be surprised to discover that you don’t actually need an extension. You might be able fit everything you need inside your existing building. Heeey presto!

However, I feel there is a place for demolition of old poor-quality building work and to rectify past mistakes, to attempt to reinstate the original building and setting etc.

The extension

The minimum thermal performance is dictated by the Building Regulations. Approved Documents Part L1 and L2 of the Building Regulations deals with conservation of fuel and power in buildings.

Meeting the minimum thermal performance requirements of the Building Regulations is getting harder [and more expensive], especially as they are regularly updated.

It’s unlikely the traditional 20th century techniques of brick and block cavity wall construction will be able to meet the new Building Regulations unless very wide cavities are used or special ultra-high performance insulation materials are used.

Using a light-weight framed structure can sometimes be easier to achieve a higher thermal performance so timber framed extensions may become more commonplace + timber should be more environmentally friendly. [See Newsletter no. 4].

What about the existing host building that you are extending

Are you proposing to upgrade or remodel part of the existing building anyway as part of the extension project?

Do you just focus on the extension and adjoining room, or do you also consider the rest of the existing house? Extension warm and comfortable, existing house not quite as much.

Many of my Clients observe that the old building doesn’t perform as well or feel as nice as the new extension, so there is a disconnect between old and new.

Therefore, do you retrofit and upgrade the affected parts of the existing building to have identical thermal performance as the extension? In an ideal world where we all have a lot of money to spend on a project this approach makes a lot of sense.

However, this isn't always possible or even recommended. The old walls will get very thick and you may not get flush plaster lines as the new walls and old walls may not line up, you may get steps in the walls.

This may also mean a major floor and / or ceiling upgrade to several rooms.

Probably more realistic to upgrade the fabric of the existing building but to a lesser standard. This is also allowed for and recognised in the Building Regulations. Panic not.

There are also damp, unexpected damage and condensation issues to consider when completing a retrofit project, or partial retrofit project.

When completing any retrofit upgrades to an existing solid walled building, make sure you do it properly with breathable [vapour permeable] upgrades. Things like a breathable limecrete floor [not concrete!] with underfloor heating + breathable wood fibre or cork insulation + lime plaster + breathable paints.

Are you planning an entire house retro-fit in the future or just certain rooms?

You need to consider what’s important on a hierarchical scale and what’s achievable on your budget. What’s essential and what’s nice to have?

An important issue to resolve is condensation risk. Not surface condensation [say on a cold pane of window glass] but interstitial condensation that occurs within a constructional build up and is much more problematic.

This is a huge topic in its own right, but let's have a quick look at this.

Interstitial condensation is where warm, moist air permeates through part of a building and hits cold air inside the construction, condenses, forms water droplets and then drips back into the building and causes havoc. Such as damp spots, black spot, mould growth, plaster and paint blistering etc.

An example could be within a new flat roof over your extension. Warm air condenses on the cold side of the insulation and drips back into the building on the ceiling.

Another example is dry lining an existing solid wall, and putting in very thick layers of insulation to save energy. The warm air condenses on the cold side of the insulation and drips back inside and creates blackspot and damp patches.

To reduce this risk a vapour control layers can sometimes be used or simply reduce the insulation thickness etc. This means the energy performance is reduced but the risk of condensation is also reduced.

It's about striking the right balance between thermal performance vs condensation risk vs costs.

To fully understand this suggest you obtain specific training on retrofitting / thermally upgrading old buildings, or speak to someone who has.

Going further, deeper + better

The Building Regulations are the bare minimum, you can exceed them if you wish. I’d prefer to do better than The Building Regulations so that energy efficiency is improved beyond the bare minimum. I do recognise this isn’t always possible with project budgets and the ever increasing cost of materials.

You also need to be bear in mind that seemingly minor bits of work may be the trigger point for a more expensive thermal upgrade under the Building Regulations.

There are also specialist standards and guidelines that standardise retrofits to existing buildings, such as PAS 2035 for houses and PAS 2038 for non-domestic buildings.

You could also consider maxing out the extension and retrofit works [and your wallet] by aiming for the certified Passivhaus and Enerphit standards.

If you decide to improve past the minimum Building Regulations standards, can you afford the extra cost or are you preprared to pay out more for the better performance and comfort levels? Will the energy and ongoing costs saved, eventually offset the extra cost of the construction? Is it worth it?

A healthcare extension project where we flipped things around

This was an unusual project for several reasons.

One of Sheffield’s largest doctors surgeries had run out of space and needed help to grow.

I helped design and deliver a new side extension to create a new Patient Record Store, Nurses Store and two accessible toilets. I also helped remodel part of the existing building to create three additional Clinical Consulting Rooms, new Main Reception, new 24 hour Night-Time / Small Reception, new Patient Waiting Area and new Staff Offices, a Flexible Multi Use Room and additional Staff Offices. Quite a few rooms to deal with!

What was slightly strange is that I had researched this building as a textbook case study of a really sustainable building, as part of my architecture degree course, and even visited, about 18 years before.

The existing building was relatively famous when first constructed in c1989 as it was a pioneering, super energy efficient building, originally designed by famous eco-architects Robert and Brenda Vale. The high levels of insulation still exceed the current Building Regulations over 30 years later and the heat required and running costs of the building are still remarkably low. Think mega thick walls + mega thick floors + mega thick roofs with vast amounts of insulation.

The managers of the doctors surgery knew this but did not want the extension to have the same energy efficiency as the old building. Mainly as they knew the cost of the new building work would be higher than if using standard Building Regulations compliant construction. So, this is what we did. The extension, while still complying with the current regs did not match the extremely high energy efficiency performance of the host building. It seemed a bit back to front but this is what the Clients wanted so this is what I helped deliver.

I also helped design a load of custom, bespoke furniture and managed to pull off some bright orange cupboards that added a splash of colour to mostly neutral coloured spaces, that used colour psychology to help keep anxious patients calm and collected.

Cost was a major problem as the Tender estimates came in above budget. The original Client wish list exceeded their available budget. I helped work out ways to save £115, 000 of costs while still delivering the core project requirements which meant the project proceeded and was successfully built. I think managing costs and budgets on projects is a newsletter topic for another day as this is a big subject in its own right as well.

This project was also a finalist for The Architectural Technology Awards 2021 [AT Awards] | Small Project of the Year.

Find out more about this unusual project by clicking here

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New places

If you are new to my newsletter then each month, I share a photo of somewhere I've been. Just sharing something about my love of buildings and nature. I also love travelling to new places and cultures. Whenever I go on holiday, I try to take a few photos of buildings and places I find fascinating and interesting. I’m by no means a professional photographer but I’d like to share some of these places with you, hopefully they capture something of what I experienced.

Last month’s photo was taken in Cuba. The building is the Edificio Bacardí in Havana. It's quite a nice Art Deco building. The Bacardi bat logo on top was a little clue. I’d always wanted to visit Cuba and went there with one of my brothers when I was a lot younger. We did a little mini road trip around some cool places, including the beautiful Sierra Maestra mountain jungle hiding place of Che Guevara. Along the way we smoked a box of fresh Cuban cigars [I’ve since given up smoking for various reasons] and drunk the best [and cheapest] mojitos I’ve ever tasted. We also didn’t see any globalised corporate chain clones anywhere, like McDonalds. An amazing country with an interesting history.

So, where was this photo taken? If you think you know where the photo was taken or like the photo and want to find out more, hit reply and let me know. Apparently, it was the inspiration for the animated kingdom in the Disney Frozen movies.

You’ll have to wait until the next newsletter to find out where this photo is from. I know, I can feel the pent up excitement from here.

What's next

Following on from the featured project, I think that next time we will have a look at how to manage your budget and control costs. There are several ways of doing this. Keep an eye out to find out more.

That’s it for now, hope you enjoyed this and I look forward to sharing more with you soon.

By the way, in case you are wondering, you’ve been sent this email because we’ve spoken in the past, perhaps discussing your project, or you have asked me a question via the website, social media or we have met in real life. I do hope you found this email helpful, entertaining and inspiring. However, if this is not the case, please hit unsubscribe at the bottom. I’ll try not to be offended, although I probably will be a little bit! I know, I know, it’s me, not you [it usually is].

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Hey super scroller, you've found a bonus video of some of my favourite places > clickity click here

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