HPH039 : Planning a Phased Retrofit – with Mark Elton from Sustainable BY Design
Mark Elton from Sustainable BY Design explains what a phased retrofit of a house entails and the steps necessary to make it a comprehensive set of measures. He also shares his views of which properties make the simplest and most cost effective retrofits.
Interview with Mark Elton
Mark Elton previously worked for ECD Architects, who had an ongoing track record in high-rise refurbishment projects. He describes this work as challenging but rewarding.
Now Mark works for Sustainable BY Design.
Phased Retrofitting is a Fall-back Option
If a whole house retrofit is the ultimate aim then there must be a comprehensive package of measures.
This will include thermal insulation, window enhancements, more efficient heating systems and some form of dealing with ventilation and air leakage.
Therefore a phased approach is one where this cannot be achieved in one hit – perhaps due to lack of funds – and so it's about focussing on the areas that can be addressed initially and then taking advantage of other opportunities as they arise later in the occupancy of the building.
A Phased Retrofit Will Delay the Full Benefits
Not only will a phased approach be more disruptive because the work will be spread out but the full benefits will not be achieved until the end when the loop is closed.
Consider Where the Trigger Points Are
When looking at a property there will be constraints as well as opportunities. So find these trigger points. For example, if a house needs re-roofing, then this might be a good place on which to focus (particularly because hot air tends to rise).
The Retrofitting Sequence Will Depend on the Building
Starting at the top of the house can often make sense. Mark says: “If you make your roof interventions the priority you can be maximising the level of insulation standards up there without affecting other aspects of your building.”
However, there are too many variables at play to generalise a sequence.
Be Careful Not to Block Future Work
There are things that can be done all along to enhance what comes later, so it's very important not to carry out any work that prevents the next steps.
In the example of renewing a roof, this could mean planning how the eaves and verges can be extended in order that the building is ready for the external insulation at a later date.
Phasing Doesn't Need One Contractor Throughout
There's no need to have one contractor carrying out all of the work through the years. This comes with the benefit of using the right person for each area – such as an external wall insulation expert or window specialist, etc.
It may also be possible to carry out some of the work yourself. Mark uses an example of lifting up a suspended timber floor, laying a support membrane and then putting in mineral wool insulation.
The Benefits of Each Completed Phase May be Palpable
Although the biggest benefits will come when all the whole retrofit is completed, there are likely to be noticeable changes with each measure.
So if a north-facing external wall were to be insulated, the inside surface of the external wall would no longer be cold. This means there won't be the radiative coolth effect that you get from a cold wall surface.
Retrofitting a Period Property is about Getting the Balance Right
Mark believes that upgrading windows can often have a big impact on reducing draughts in older buildings but there is a balance to be struck. While a conservation architect might see original windows as sacrosanct other architects feel that energy saving is far more important.
Extensions Mean that There are New High Standard External Walls
If you're planning to extend a property then this should also be a priority of the phased retrofit because the external walls of that extension should be built to the highest possible new build standard.
Doing it the other way around might lead to a new heating system that isn't sized to accommodate the new extended property.
Certain Measures are Needed Together
For projects aiming for the EnerPHit or Passivhaus standard, the airtightness and heat recovery should be addressed together because there's a symbiosis between them.
If the heat recovery ventilation has been commissioned before the airtightness has been dealt with, there will not be the efficiency gains. Conversely a super airtight building with no heat recovery ventilation system (or some form of mechanical extract ventilation) will not lead to a healthy environment.
Ventilation Needs Upfront Thought
Ducting for the heat recovery mechanical ventilation for most retrofits can be done at high level.
If planned correctly the duct runs should be fairly short and in the corners of rooms.
Mark says: “You’re just boxing out at high level. Typically you’re going to try and do that in the hallway or above cupboards, above toilets so that its impact on your main rooms is minimal. Then you just need to identify suitable space for the heat recovery unit itself. It really needs to be on an outside wall in an insulated cupboard of some kind.”
Exploiting Design Opportunities Could Help Fund the Retrofit
As mentioned earlier there will be opportunities with each property. Sometimes it is possible to add value to a house by altering the layout or adding space, so the retrofit would be the perfect time to do this. They’re not mutually exclusive and quite often one triggers the other.
Retrofits are an Upfront Investment
One aspect of retrofitting that can be difficult is that it tends to make more sense if you know you're going to be living in a property for many years.
Currently energy efficiency measures do not seem to be reflected that much in the value of a property but this is likely to change.
Marks Tips for Finding a Suitable Property to Retrofit
There are certain properties that Mark believes are easier and probably cheaper to retrofit.
Mark says: “I would tend to look towards properties that you can externally insulate. It’s an easier, less disruptive process. It retains some of the thermal mass of that building on the inside. There are less tricky issues to do with interstitial condensation to deal with. So if you’re looking at a property to retrofit with external wall insulation clearly you’re looking for not too many obstructions on the outside, perhaps an overhanging eaves that has plenty of scope for that to work with windows that are sub optimal and you’re going to have to replace anyway so I can do that at the same time as my external wall insulation. Perhaps one with not too many single storey extensions and too many bits and pieces stuck all over the side.”
It must be something that's fairly rational that a planning officer would not object to an external render being applied, so perhaps it's already a white rendered building.
Energy Efficient Bolt-holes are Not So Practical
When Ben proposes that in larger period properties the owners could create small energy-efficient bolt-holes Mark says it would be difficult to make these reach the Passivhaus standard. This is because of the form factor.
As buildings get smaller there’s a lot more surface area than floor area so it’s much harder. Mark uses the analogy of a baby keeping warm. Babies get cold because they’ve got a small body mass for a big surface area. As we get bigger the reverse is true.
Retrofitting at Scale Would Make the Most Sense
In an ideal world whole street retrofits would be the most cost effective approach.
If neighbours agreed on the scheme there could be a single planning application and one contractor could do the whole job.
In practice this is unlikely to happen.
Work Carried Out Should Easily Last Until All Phases are Complete
If the phases were spread out over a few years there is unlikely to be any concern over whether the products would deteriorate. This is because components such as insulation and triple-glazed windows are going to last 60 years or longer if looked after.
We are not talking about products with moving bits that often have much shorter lifespans.
More Resources Available Today
Knowledge on retrofitting is increasing with each project that is being carried out.
There are also good resources for self-builders wanting to tackle a project. For example, there are Haynes manuals on creating eco homes or showing how to insulate a house.
Post War Building Stock Needs to be Upgraded to the Best Standards
Mark believes there needs to be an overview of the building stock in the UK.
While there are great older buildings that are the cultural heritage there's also a lot of post war housing stock that’s perhaps not so loved.
Mark says: “The heritage stock we want to hold onto. We don’t want to retrofit it to the extent that it damages those properties but equally we do want to be able to improve the comfort for people that are living in that stock. Post war housing stock on the other hand, I really think we should be looking at every opportunity to go to the very best standard on that, to EnerPHit standard or Passivhaus standard, to compensate for all those heritage properties”
Overarching Government Goals are Lacking
Mark concludes that the bulk of retrofitting is being instigated by individual organisations, building owners or social landlords but nobody is setting targets and looking at the bigger picture. This is really only something that the government can do but currently this vision is lacking.
Mark helps answer a couple of listener questions. Jon Mason wanted to know about the most logical way of phasing a retrofit while Tim Shepherd wanted to find out which parts of phased retrofit have the largest wins.
Find Out More
Download a transcript of the interview with Mark Elton.
The Property Podcast
If you're looking to invest in property, Ben wants to recommend a podcast to you. He has recently been listening to Rob Bence and Rob Dix on The Property Podcast.
This has some great insights into how to get started in the UK market, but a lot of the information is relevant to any property investors. Rob and Rob produce a concise and fun show which is well worth a listen.
Our Question for the Comments Section
Is a phased retrofit an option that you would consider?