In a previous life I designed and managed the implementation of
new retail store spaces which gave me just the tiniest taste of how rewarding it must be for
an architect to see their creation move from a concept on paper or screen all the way through
to a fully built end product. You do get a tangible result that brings a huge sense of achievement. I
guess that's why so many architects prefer to create brand new structures from scratch. And as
we saw in our recent video about Passive House standards, new builds also offer the opportunity
to include the kind of energy efficiencies that'll be crucial to a more sustainable future.
But there's another stream of architectural work that's much less glamorous and arguably
far more important from an environmental point of view, and that's the enormously difficult
task of retrofitting existing buildings. According to the website 'Architecture 2030'
existing buildings generate nearly 40 percent of annual greenhouse gas emissions and
about two-thirds of the buildings that are standing today will still be there in 2050.
So this week I'm having a think about how the architectural and building industry is responding
to these big challenges and what the average homeowner can do to create energy savings in
their existing property to get themselves moving towards that all-important Passive House standard.
Hello and welcome to Just Have a Think. I'm sure quite a lot of you folks watching this program
will, like me, have dreamt of creating your perfect living space at some point in your life.
But not many of us will ever get the opportunity to build our own home from scratch.
And of course there are others who love the home and neighbourhood they're already living in
and wouldn't want to move anyway but who have houses that don't meet any of the
energy certification requirements and that are costing them a fortune in fuel bills each year.
And then there's the rapidly growing number of people living in rented accommodation and social
housing as a result of the societal move towards greater urbanization and the relentless rise
in property prices. The vast majority of those buildings will need to be radically overhauled
as part of the global drive towards greater sustainability over the coming decades.
So retrofitting looks set to become a crucial activity, not just for private owner occupiers,
but also for landlords and municipal authorities. Retrofitting isn't just about bolting some add-ons
like solar panels to your roof to reduce your electricity bills, although that is an extremely
good idea in its own right. No, it's really predominantly aimed at greatly reducing energy
consumption in the first place by significantly improving the fabric of the building itself
to increase its thermal performance and comfort. The challenge is knowing how far to go and how
much comfort and performance any retrofit measures will genuinely deliver. The industry bods have
two levels of improvement that they generally refer to. The first is called a shallow retrofit,
which is fairly superficial, and may only mean bumping up the insulation in your loft and
fitting a more efficient boiler. The second level, unsurprisingly, is called a deep retrofit and it's
a whole different ball game altogether. So how do you know which category your works fall into and
what standards are in place to assess them? Well we already know about the Passive House standard
but it's almost always physically impossible to reach that lofty goal in an already existing
building that wasn't designed that way in the first place, so some allowances have to be made
and those are reflected in a globally recognized refurbishment standard called EnerPHit, and a couple
of European spin-offs called OutPHit and EuroPHit ( see what they did with the PH there? Genius!) In
existing buildings architects are limited by geometry, orientation and structure. There may
also be thermal bridges that are difficult to completely eliminate and that provide a path for
heat to escape through gaps in existing insulation. The EnerPHit standard takes all that into account and
sets a lower performance level than Passivhaus which can be summarized like this. The building has
to achieve a space heating and cooling demand of 25 kilowatt hours per square metre per year
compared to the 15 kilowatt hours per square metre per year required for Passive House certification.
It also has to reach an air tightness of one air change per hour instead of 0.6 under the
Passivhaus standard. So retrofitting is not easy and while EnerPHit is not as strict as
Passive House, it's still a pretty tough standard to achieve. The first thing to aim for is a high
level of internal or external insulation, not just in the walls, but also below the ground floor and
in the roof spaces. Retrofitters have to calculate very carefully where to install insulation to
achieve the best results without causing other consequential problems. That's trickier than it
sounds. For example if you just stick a bunch of insulation on the interior side of a wall
you might make the room warmer but you'll also inevitably make the external wall
colder. If that wall is made of a porous material like breeze blocks or some types of brick
then you could be blocking off its ability to get rid of moisture, which can result in damp
and mould - which you don't want! So if an external wall is very exposed to the elements then the
internal insulation may not be your best bet and you'll probably have to consider adding a layer
of insulation onto the outside surface which will then typically require a rendered finish.
You'll also need to install high performance triple glazed windows and external doors,
and the designers will usually need to consider how they can make significant improvements to
the insulation and taping around the window and door frames and cavities as part of any
new installation. Once you've achieved these improvements in the sealing of the building
envelope, then just like with Passivhaus design a mechanical ventilation and heat recovery
or MVHR system will need to be installed. You may also be well advised to replace your existing
heating system with a ground or air source heat pump, which is something we've looked at a couple
of times on this channel, and I'll leave links to those videos in the description box below here.
If you are going to take the plunge though and go through the pain of gutting your home to
make these major investments in future proofing then there's probably not much point in skimping.
The benefit of using the EnerPHit certification as your benchmark
is that you'll be forced to comply with the rigour and quality assurance that the standard demands.
That means you'll likely need to employ an experienced team of designers and builders
who know how to carry out the works to ensure that the air tightness performance is achieved
and that there are no hidden shortcuts taken at any stage in the process. The EnerPHit certification
process is exactly the same as Passive House certification. To meet the requirements the
project must be designed using something called the Passive House Planning Package or PHPP,
which is a software-based calculation tool used by architects and planners to assess a building's
heating cooling and primary energy demands and recommend appropriate levels of remedial works.
And the finished project has to be certified by an accredited Passive House certifier. The cost of
an EnerPHit retrofit will obviously vary greatly from building to building and from country to country
so if you're thinking of embarking upon a project then you should seek the advice of
your local Passivhaus organization. Fortunately Passivhaus is now pretty much a global standard
so you should have no difficulty getting guidance for your own project,
and again I'll leave links to some of those websites in the description box below.
As a very rough rule of thumb though according to the UK home building and renovation website
a deep EnerPHit standard retrofit budget will likely be somewhere between £800 and £1000
per square metre with an MVHR unit installation for an average size house coming in at about
£10K and triple glazed windows and doors costing around £400 to £600
per square metre. The bulk of the rest of the cost comes from the labour intensive
work to install all the insulations, membranes and intricate tapings around protrusions and junctions
that ensure the air tightness measures required to get certification. That work is very time consuming,
and it has to be done with great care because much of it is covered up after it's completed and you
really don't want remedial works at the end of a project like this. There's no question it's a
big financial commitment but depending on where you live there may well be grants and incentives
available from state or national government. Over in Ireland for example homeowners can get as much
as 50% of their retrofit costs subsidised by that country's Sustainable Energy Authority,
and that level of central funding is really something that needs to form part of the green
recovery plans in every developed nation in the world. A deep retrofit project can take a building
from an energy performance certificate rating as low as F or G, which is basically a damp leaky
shell that's impossible to keep warm in cold weather, all the way up to an A-rated home that
comes somewhere close to the energy efficiency of a purpose-built Passive House construction
potentially reducing energy demand by 80% and carbon dioxide emissions by 90%.
People who've gone through the process talk about the transformation in their comfort and health,
with a constant year-round ambient temperature within the whole home, and a lovely crisp clean
air supply from the ventilation system, all achieved with negligible heating and cooling bills.
And of course once you've got your official certification you will have significantly improved
the value and marketability of your home. In truth the world is miles behind where it should be in
applying these energy saving measures to domestic and public buildings, but awareness is growing
and the EnerPHit standard is gaining traction in many parts of the world.
Examples of successful retrofits are easy to find online at websites like Passive House Accelerator
who've got an entire section specifically dedicated to case studies from all over
North America and the wider world. I'd highly recommend this interview with James Traynor
from the Royal Institute of British Architects, who's written a book all about the EnerPHit standard.
And of course there are numerous YouTube videos showcasing successful retrofit projects
from the United States, Canada the UK, Europe and Australia, to name just a few.
And many local authorities are now also beginning to understand their obligations
as part of the climate emergency to invest heavily in major improvements to their social
housing stock, much of which hasn't been touched for decades. Some of those buildings have become so
badly insulated and leaky that the residents simply can't afford to pay the huge cost of
heating their apartments properly. The consequence of that is a level of persistent cold and damp
that in many cases is causing chronic respiratory illnesses in long-term tenants. We talk about some
pretty amazing technological breakthroughs on this channel which will no doubt be very important for
reaching net zero carbon emissions by 2050. But many of the best solutions don't rely on fancy new
machines or ambitious and unproven geoengineering concepts. They're right in front of us - hidden in
plain sight as they say. Investing rapidly, efficiently and effectively in our existing
buildings and national infrastructures will not only massively drive down greenhouse gas emissions
but it'll also create hundreds of thousands of well-paid jobs for at least a generation to come.
Now, if you've been through a deep retrofit yourself and you've got some top tips that
others could benefit from, or if you have direct experience of working in the Passivhaus and deep
retrofit industry, then dive down to the comment section below and leave your thoughts there.
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