Will South from Etude takes us step-by-step through the retrofit of his Victorian terrace house in Brighton, which has improved the health, comfort and energy efficiency of the property.
Interview with Will South
Will is a mechanical engineer, working at Etude to make buildings better through reducing energy consumption and carbon emissions, an approach he has carried over to all the places he’s lived. With his most recent move he had in mind a retrofit project right from the start. He wanted to be in the middle of Brighton, close to the railway station and the coast, in a modest sized home. So he chose a Victorian terrace house, originally a two-up two-down that he could retrofit to the level that would be right for the building.
Many period properties have common traits
Will’s house is a classic Victorian terrace design, where there is space for you to take off shoes and coats just through the front door, the stairs are in front of you, then there’s the living area on one side and a kitchen all the way through at the back. Upstairs, there are two bedrooms and a bathroom. Will describes it as a simple layout with a nice flow and high ceilings, even upstairs, which is more unusual.
Deciding how deep to go with your retrofit is a personal choice
A big part of Will’s day job is working on Passivhaus projects, but here there was a question around the right level of retrofit for this type of property.
This project has also made him realise that maybe not all homes need to have as deep a retrofit as he used to think, and that heat pumps are more than capable of heating the majority of homes with few changes. However, he knew he wanted to take it further and make the house as comfortable as it could be. With his experience in ventilation systems, glazing specifications, insulation, etc. nothing was off the table.
“We’ve done everything: walls, roofs, floor, new ventilation system, new windows, but a lot of it is as an experiment to show how it could be done.”
Watch an EnerPHit retrofit of this Victorian home in The Hub.
Decarbonise your heating by moving to a heat pump
One key move Will wanted to implement to lower his carbon emissions was to switch from a gas boiler to a heat pump. For most homes, some fabric measures may be needed, often topping up loft insulation, improving windows and upgrading radiators. Anything after that will continue to improve comfort levels, reduce bills and increase resilience for the future.
Create an overall plan for your retrofit
Will started with his dream end point, irrespective of budget, to come up with an overall plan for the retrofit. For example he has not installed solar PV as part of the project but he has made allowances for it as a future addition.
With a solid retrofit plan, he then examined the priorities. There was leak in the roof and a rear extension, where the floor and the roof were in a sorry state. Generally, starting with the roof is a good strategy, which for him meant redoing a parapet then making sure the party firewalls and the chimneys were in a good state before he did anything else, so that the building had a good chance to stay dry.
Having a good ventilation strategy is essential on a retrofit project
Will tells us that although it took a long time he ended up doing everything in almost one go. If you have to do a phased retrofit, you need to make sure that the building is left in a good working state at the end of each stage. The main risk is around ventilation and managing moisture in the building, and you need to be careful you don’t seal up the building or insulate it in one part without dealing with the ventilation. A ventilation strategy is often a priority and if the end goal is a mechanical system, then get that in early, so you’re already managing the moisture levels.
SketchUp was used to create drawings for the project
As a consultant Will knew what was needed but he wasn’t used to doing the drawings himself, so that was a bit of a challenge. He used SketchUp to create a model of the house, including drawings for the existing building and the proposed building. Being in a conservation area, planning permission was needed for replacing windows at the back of the house, and altering the roof-scape slightly to fit the heat pump at the rear, which led to more drawings for the planners. In the end he made a full set of drawings to help him work out what he was going to do and allow him to communicate easily with the contractor.
Will imagines that in the future there will be templates for every building type, that you would alter to reflect your own situation. There’s already a good website called retrofit.support, which has a pattern book of details that give you a place to start.
Create a detailed cost plan
Will paid a cost consultant who specialises in housing to provide him with a full cost plan. This gave him a long list of everything needed, with a starting point for all the prices, giving a good feel for what it would cost if he did everything. This service cost around £400 but was invaluable.
The costs for construction broadly came in as expected. He imagined that there might be a big cost differential between materials but in actual fact he was dealing with such small areas that the cost was all in the labour.
Budgeting for the internal finishes was much more difficult as costs varied dramatically, particularly for bathrooms and kitchens. So unless you have an example of the product that you want to use, it can be hard to budget accurately for this stage.
Different insulation strategies have been used around the house
Will explains that even though it’s a small building a variety of strategies have been needed to insulate the roof, walls and floors. Initially they planned to live in the house while the retrofit took place. The first phase was going to be the rear return, with the kitchen and the bathroom. The kitchen ceiling was falling in and the bathroom ceiling looked worrying, so both needed attention.
The building has all sorts of roof types, which is not ideal. There is a small parapet at the front which has got insulation between the rafters and a lead roof. Then there’s the main loft which has mineral wool insulation, the rear return which has Larsen trusses, filled with insulation in the pitch, and a small flat section of fibreglass roof which has got the heat pump on it.
“Generally, starting with the roof is a good strategy. An old fashioned building has a good hat and good boots.”
Planning restrictions also had an impact on the insulation strategy
Being in a conservation area an internal wall insulation strategy was adopted at the front of the building, using 80mm wood fibre board. There is a bonding coat underneath, made by Baumit, which helped create a flat base for the boards to go on to and added an extra 10-20mm of insulation.
At the rear of the property they were allowed to insulate externally and have used cork, which was chosen because it deals with moisture better than some other products. The external wall insulation is taken below ground to the foundation with EPS.
The floor became a bigger project than originally planned
While Victorian properties are highly desirable today, when they were built they were thrown up quickly and cheaply so there were a few surprises lurking. When they took up the floor, they found slim 3-inch joists sitting on continuous bungaroosh, which was just piled up chalk. As they were able to move out of the house for a few weeks they could tackle the floor in a more significant way.
It involved taking out all the timber and the dwarf walls, scraping back the chalky base to create the space needed for the floor build-up. EPS was directly put onto the sand blinding, then a plastic DPM, and finally a concrete screed with underfloor heating. It’s a simple build-up as there’s no structure sitting on it. Will would have liked to have reused the original floorboards on top of the screed but was advised against it.
The sash windows have been improved
While Will had more freedom at the back of the house, where he installed some triple-glazed units, at the front of the house there were restrictions. He also did not want to get rid of the beautiful period sash windows. So he has replaced the sliding part of the sash and put in vacuum glazing. The boxes are original although he has added a draught strip to improve airtightness. He’s used a foam filled rubber draught strip, a type more often used on a casement window, which is more robust and gives better airtightness, but it makes the windows a bit stiffer. As all the windows are wooden, they will need maintenance and Will suggests to always repaint them just before they look like they need painting!
Having a continuous airtightness layer was easier said than done
The strategy at the beginning was to identify where the airtightness line would be for each part of the construction. Will realised that they would be able to achieve it for some parts, but in other areas they wouldn’t be able to get into places to create an air barrier. He estimates that he got around 75% of the way with airtightness and to get any further would probably have meant gutting the whole house and starting again. The intermediate floor and all the internal walls stayed where they were, but the external wall finishes were removed allowing for bonding of the insulation, creating continuous runs to tie into the next airtightness material and into the windows. The damp proof membrane underneath the screed on the ground floor comes up the inside of the wall and is taped on there. In the loft Will put a membrane over the top of the joists, cut it around all the trusses, taped it and then put the loft insulation on top of it. It was very difficult to tie it into the top of the walls right into the eaves where access was limited. The eaves were extended very slightly at the back of the house to accommodate the external wall insulation. This meant the last two tiles were off for a time and Will used the opportunity to do more taping. His approach was to use membranes only where there was timber, and then everywhere else to use a wet lime product.
Before the sash windows were replaced, Will got an air permeability of 2.1 which is three air changes per hour at 50 Pascals, which he was pleased with and was in fact the number he’d put in his PHPP model. He hopes it will have improved and is going to get another air pressure test and more thermography in the winter.
MVHR can usually be integrated seamlessly into an existing home
Installing mechanical ventilation with heat recovery can really improve the indoor air quality in an existing dwelling. It manages moisture in the home, allowing you to do things like cook or dry washing without consequences. And Will believes that there is always a way of designing a system into an existing home and figuring out the duct runs, etc. It just takes careful planning.
The benefits of MVHR are noticeable even in a leaky home
Even if the airtightness has not been addressed fully Will feels that installing MVHR will improve the ventilation in a house and because it has 90% heat recovery it will give some energy saving no matter how efficient your building is. If you then improve insulation and airtightness you will continue to see benefits.
A heat pump is a good choice for a low energy home
When they bought the house it had a 10-year-old combi boiler, which they could have used for a bit longer, but Will was keen to switch to a heat pump heating system. So when redoing the bathroom he took the opportunity to put a new hot water cylinder where the boiler was, because all the pipe runs link to that point. An extra motivation to get off gas was the massive gas meter that was located in the entrance hallway. He paid extra to get this disconnected and removed.
In Will’s experience it was difficult to buy the heat pump and difficult to get it installed, a view that other people have also expressed. At the time, it was also difficult to find somebody qualified to install heat pumps. In the end, his builder’s plumber carried out the work, and used it to upskill and get his MCS qualification, which was really positive. On the negative side, he hadn’t known they didn’t have MCS and so he was not able to get the boiler upgrade grant.
He had assumed that the heat pump manufacturers would know what was needed for a small home, so hadn’t looked into the detail himself. That was a mistake and the whole process got complicated very quickly. They’d assumed he wanted thermostats in lots of different places, and that the radiators and underfloor heating circuit were on different zones. Will ended up having to change things afterwards, which was frustrating. The other eye opener was just how much equipment you end up with inside the house. He had thought about a cylinder, but with unvented cylinders you also have an expansion vessel for the heating, an expansion vessel for the hot water. Then there are two control boxes, two zone valves and they wanted to put in a buffer vessel as well. It really started adding up, with a lot to fit in a small area. He recommends buying a hot water cylinder with a built-in expansion vessel, which is a bit more expensive but saves on space.
Will’s energy consumption has gone down significantly
The average temperature within the house has increased to a constant 20 degrees, which is where Will wants it to be. Gas consumption has gone from 158 kilowatt hours per metre squared per year, which was quite high, to zero.
This has however been replaced with electric heating, with electricity use now around 40 kilowatt hours per metre squared per year. This went up about 20% after the switch over to electric heating, so a much smaller uplift than the reduction in gas. By Will’s calculations his carbon emissions are down by 85%, which is significant. If solar PV was added at a later date they could be net zero.
Some of this is about how they live, with just two people in the house they don’t have huge consumption and are out a lot of the time. In financial terms their energy costs have more than halved, reducing from £2,500 a year to about £1000 a year.
Sticking to a budget is tricky!
Will sees a budget as a good tool to manage costs although he realises this isn’t necessarily what you’re going to spend. Therefore he put aside a significant contingency. For him this takes away the worry about money, which can so often cause problems.
Buying a smaller house in the first place and securing a bigger mortgage so as to free up the cash was also sensible. They had an inheritance and some savings, which essentially has all been spent on the house. It has come in at around £150,000, but this figure includes a new kitchen, new bathroom, new flooring and a lot of extras.
Replacing the suspended floor was a gamechanger
Amongst the takeaways from the project Will feels the hard work and disruption of putting in a solid floor with insulation underneath has really paid dividends. So if you have enough space to play with then this is something Will would definitely do again as it’s made it draught-free and always comfortable to walk upon.
The installation of the heat pump relied heavily on the plumber
Will was surprised that even though they had a Vaillant heat pump and used their designs, a lot still rested on the plumber. If he was doing it again Will would take more of it under his control.
Airtightness is often about doing the best you can
Will thinks he did a really good job on airtightness, but reflects upon the fact that there is always more that could be done. If he were to do it again he would use more traditional wet materials like lime-based plasters for airtightness when dealing with crumbly brickwork.
The house is now comfortable all year round
When they bought the house the structure was worrying with a bendy beam, ceilings falling down and it was very damp, with slugs behind the kitchen cabinets. During the winter they were just heating whichever room they were in and downstairs they were always aware of draughts from under the floor. There is none of that now, it feels homely and is a constant 20 degrees throughout the house all year round.
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