Retrofitting to Passive House standards

Passive House, or Passivhaus, is an energy efficient building design standard for new builds all over the world. But what about existing buildings that already account for almost 40% of all global greenhouse gas emissions? Can they be upgraded to the same level?

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Previous Just Have a Think videos

[Lewis.Alcindor]

Thanks for the video! I can give some tips from a Passivhaus and building science perspective.

In terms of "bang for your buck", here are the main goals for new or retrofit builds is as follows:
- first define the entire thermal envelope. Know where it connects to your windows & doors. Know how it connects transitions between one floor to another, or the top floor to the attic & roof.
- Thoroughly air-seal the entire thermal envelope. You will need to run a blower door test prior to closing up your walls to make sure your air seal is good and complete.
- Super insulate the roof and/or attic. This is where most of your heat will escape in the wintertime via the stack effect.

In terms of other work, insulating your exterior walls and installing new triple-glazed windows is optional IMO. The most effective work was to air-seal the walls, since air leaks are where much of the heat escapes in the winter or comes in during the summer (at least for exterior walls).

Air sealing provides two benefits:
- prevents hot air from coming in during summer, or warm air from leaking out during the winter (which feels like cold drafts coming in).
- prevents moist air from coming in during the summer. If you keep your space air conditioned all the time in the summer, much of the humidity issues are due to air leaks in the thermal envelope. Air-sealing allows your A/C to cool the air effectively without making it feel too clammy.

High performance windows and doors are necessary if you dramatically increase the insulation levels of the exterior walls as well. This is because poor performance windows will act as a thermal bridge in an otherwise highly insulated wall, which ends up dragging down the overall thermal performance of the whole wall (windows included). You should install the best (lowest u-factor) windows you can, though technically speaking, the best windows have the same thermal performance as a lousy wall (roughly R4-8, in imperial units).

I would also suggest the MVHR systems as suggested in this video. Indoor air quality is a topic that is becoming more well-known and important to people. MVHR systems are designed to run constantly to provide fresh filtered air to occupants. They have heat and/or humidity recovery cores that exchange heat and/or moisture. This warms the fresh air coming in during the winter, and cools the fresh air coming in during the summer.

MVHR systems are supposed to be separate from heating and cooling systems. You could combine the two, but it's more efficient to have a separate mini-split heat pump to cool and heat your home.

[NeilStansbury]

If the UK was serious about building performance they'd zero rate VAT on energy performance products like insulation, airtight membranes, tapes, HRVs etc etc, and then mandate that so-called "builders" must have at least basic training on concepts like thermal bridging, air tightness, thermal mass and interstitial condensation. As it stands, the UK domestic construction industry is a joke when it comes to high performance buildings. My personal journey has been as a non-construction engineer teaching so-called "experts" how to do do their jobs properly. If we're serious about these standards, then there needs to be a fundamental change in this industry.

[Tennisbull-match-statistics]

My California home built in 2002 was very drafty. I spent countless hours adding weather stripping and filling holes in walls and ceilings with foam and chalk plus adding more insulation and a solar barrier in the attic. It was well worth the effort

[jainger]

A step in the right direction would be to strengthen building regulations on all new build houses. My daughter has just bought a new house and it must be the coldest and draftest house I've ever been in. Costs a fortune to heat and this house should be about for the next hundred years. It's like buying a steam powered car. So far away from a house for the future it's criminal.

[lesliegweir]

I acted as the general contractor in the building of my own house many years ago. It wasn't built to the passive house standard but it was fairly well insulated. R20 in the walls and R40 in the attic. The basement was finished at the same time as the other two floors, and was warm enough in the winter that we didn't heat it much and used to play ping pong down there. This is in Ontario, Canada.

[danielmadar]

Thanx for your work.
We live in Israel, so our major concern is heat and humidity. 11 years ago we've retrofitted a 40 years old concrete house into a passive house. We replaced the asbestos roof with an isolated panels roof, insulated the concrete walls (thermal mass) with straw bales+lime plaster, changed the windows to double glazed polarized glass + aragon gas, used concrete floor tiles (thermal mass) over fine gravel (instead of over sand), and shaded the windows. The insulation wraps the concrete (thermal mass) from the outside.
Before the renovation; during the summer, the roof used to radiate strong heat until 02:00 every night; during the winter, the whole house was constantly cold. After the renovation, the house if comfortable most of the hours in the year. During the summer we turn on the air conditioner only to lower the humidity in the afternoon. Last winter, we used a tiny electric radiator to heat up the whole house during the nights. Our electric bill dropped by ~70%.
This year, after 11 years that bureaucracy obstructed us, we have finally started to install solar panels on our roof (20.03 kWp), which is 3 times larger than what we use. The rest we will sell to the grid. Here we get per kWh we produce, ~85% of the cost we buy a kWh- a great incentive.

[MatthewHarrold]

I moved from a house built in the late 70's costing around $3k per quarter in electricity to a new build 6 years ago with an electricity bill around $900 per quarter. This includes moving from no AC to a heat pump, and a wood heater to the aforementioned heat pump. It also includes my 4 kids getting older and utilizing more gadgets and computing. No more chopping/stacking wood, no more sheltering in retail shops on extraordinarily hot days for sweet relief from oppressive heat, or going on a pointless drive in my car with AC. We weren't even striving for passive, and aren't close to that standard. We rate around 6.5 stars on the Aussie scale. First version. We will improve. $0.02

[lesterstanden]

I'm just installing a DIY MVHR system in a small one roomed house that I built last year. I've sourced all the MVHR components for under £500 and the building services engineer who supplied the heat exchanger calculated that I'd achieve 83% heat recovery. The MVHR unit uses about 2 Watts supplied by a 12 Volt power system that is itself powered by one solar panel and a micro wind turbine. It will cost nothing to run (I'm off grid). My point here is that you can do DIY MVHR and keep the costs down.

[ianjenkinson]

A key issue that needs to be considered is that many homes in the North of England do not have sufficient 'market value' to justify the cost of extensive refurbishment, let alone retrofitting to 'Passivhaus' standard. Retrofitting is far more difficult and expensive than it initially appears and achieving a 'quality' outcome is rarely guaranteed. I have dealt with the repair, maintenance and upgrading of some large housing estates in several parts of the UK. With a typical contract of 500 homes per renewal period, the economy of scale was considerable but even then the costs were high. You may recall the 'Housing Market Renewal' programmes in the older Midlands and Northern industrial cities some years ago, even then it was much cheaper to demolish and rebuild to an a far better (but not Passivhaus) standard than to attempt refurbishment. If it was unaffordable for Social Housing schemes I doubt that private landlords will be interested.

[volkhen]

Thermomodernisation is very popular in Poland. The most popular method is to glue EPS boards on the outside walls, then first layer of cement plaster is put, then nylon net is put onto wet plaster. Then second cement plaster is put on the net. After it dries the last layer of plaster is put which is composed of little stones 2-4mm which are in colored “cement”.

[whatwouldbenice]

I would love to start building passive houses. As soon as this 'conventional' building degree is over that's where I'm headed!!

[brianmombourquette]

We owned a century home in Halifax NS. It had blown in cellulose insulation in the walls, and some fiberglass in the roof plane. After years of drafty winters, we beefed up the insulation in the lofted attic (more than doubled it), insulated the basement and rim joist, added weather stripping to the windows and doors, and replaced single pane with double pane as needed. Plus we installed a new boiler. We cut our fuel consumption by at least half, and we had a much more comfortable house. This would have been a shallow retrofit by your standard, but it was a night and day improvement. Well worth the time and money, and added value when we sold.

[daviddunmore]

aout two years ago we converted the attached garage to a habitable room. 10cm foil covered foam sheets in the floor and walls and 60cm fibre/wool insulation in the loft. new double glazed window and French doors. it's now noticeably warmer then the rest of the house (2000 build). We also have about 45cm insulation in the main loft and insulation in all the stud walls. Oh, and the boiler is only four years old backed up with a whole new central heating system, The house has been neglected by the previous owner for several years to the point that we had to replace all the taps, the shower and many other things.

[rbdogwood]

I found the most effective components were exterior cladding and a ground source heat pump. The house is an 1890 detached pair of miner's cottages, so since I bought it semi derelict 30 years ago I've used most of the obvious methods, and found that most of them go out of date quite quickly. My advice is do what you can as you go and don't worry about catching up with technology as you never will. Perhaps the best bet after all is to replace existing buildings with passive houses, but since that is impractical I am just running the house on renewable energy and apart from the occasional chainsaw for diseased trees have more or less eliminated fossil fuel.

[rogerbarton]

A friend of mine is an architect, I don't know how pleased he feels when he finishes a project but I wouldn't be seen dead in one of his buildings. He designs mortuaries.

[impamiizgraa]

You don't know how much of a difference energy efficient building design makes until you've lived in it. I am moving out of a B EPC-rated new build, triple glazing, insulated walls and floors (and it has South and South-East aspects with big floor to ceiling windows). I turn on the heating a few days in winter, max.

I've just bought a Victorian terrace with a rating of D and the first thing I hope to do is retrofit some energy efficient insulation and other design features to try to get it close to what I had before, but it won't 100% be the same.

[aeae]

When the exterior of a non-brick building is being updated, such as when siding is being replaced, is a good time to explore upgrades. Insulation can be added to the exterior that is a continuous layer, which is much more effective than the usual batt insulation. The great part is also that exterior insulation also won't cut into living space.

That said, no reason to wait increasing attic insulation. But don't forget that it's important to air seal before insulating... if there are lots of leaks in the attic that carry air through the insulation, then the insulation is doing little good. In fact, a decent sized attic can be air sealed with a spray foam gun and a 5 cans of foam for a hundred dollars by a DIYer, which will be easier for homes with batt insulation (blown insulation makes this work much harder). This is an energy upgrade that will pay for itself within a year or two. It's also kind of fun and is something I did on our previous home. :)

[bilgyno]

We did a deep retrofit of a 1938 house in Holland last year. Every installer told us it was impossible with an old house like that, but we persevered and succeeded. The biggest problem is the conservative attitude of the average installer who doesn't know about heat pumps, ventilation, insulation etc.

[snowstrobe]

I live in one of those social housing towers, a true abomination. The floor/ceiling is a single slab of externally exposed concrete. It's ice cold all winter. In winter I can only afford to heat one room, so I sleep in the lounge, and even that triples my bill. The whole place is riddled with mould, and it's a constant expensive battle to keep it under control. Even the curtains move when the wind blows [which it does a lot here]. I have tried to reseal them, but lack the skill and equipment to do so properly. The council couldn't care less. My wall heater broke in the winter and I was told it was not a priority, it is still broken. I don't think buildings like this are savable, they just need to be knocked down, they were built cheaply in the 60s and were never meant to be used this long.

[rickrys]

Great advice. I was lucky to build a house in the US to PH standards. It occurred to me that If I could have taken half my new insulation and roles of sealing tape to an old house, the amount of energy that could be saved on a leaky old New England antique home would be maybe 5 times the smaller amount of extra energy my house would use. A new house like mine used lots of new virgin materials and a fair amount on concrete and other energy intensive products too. Bringing an old home to EnerPHit is certainly expensive but should be even more satisfying that realizing you new home dreams.