Did you smell when you walked into the house? It smelled like home.” Lars Boelen is in a terraced house in Roosendaal because the residents want to make their house more sustainable. You expect it to be about solar panels, cavity walls, insulation, double glazing. Not about the smell. But Boelen, the self-employed person who is helping to make a plan for an energy-efficient house on behalf of the municipality, hardly talks about solar panels.
He talks about smell. About fresh air, ventilation and infiltration, particulate matter and excessively high CO2concentration in the home – and that improvements in air quality go hand in hand with energy savings. “What is good for the indoor climate is also good for the outdoor climate.”
Boelen, who lives in Weert herself, advises municipalities in North Brabant in particular on making homes more sustainable. As a self-taught ‘home whisperer’ (he came up with the job title himself) for five years now, he has been giving tips on how homeowners can reduce their energy consumption.
His working method stands out because he approaches it differently from the outgoing cabinet and the parties behind the climate agreement concluded in 2018. Boelen has little interest in commercial heat networks or wrapped facades to make houses natural gas-free. Homeowners can achieve the most by renovating their own homes step by step, he believes. Close gaps, ventilate better and insulate efficiently with plant materials. It is an approach that puts living comfort first and puts residents in their own hands. “I’m very optimistic that everyone can fix it themselves.”
He is carrying out or carrying out ‘knowledge and learning programmes’ for a dozen municipalities. The municipality pays Boelen to examine a few homes, many of which have been built locally, so that housing associations and private owners can benefit from the knowledge gained.
Energy leak in the roof
The house in the Roosendaal district of Langdonk that, according to Boelen, smells like home, is such a house. It is the terraced house from 1971 where Peter van den Bosch (64) and his wife Karin moved in a month ago. Tens of thousands of these were built in the Netherlands during that period. Bare and functional, garage in the spacious front garden, kitchen window next to it. Energy label E. “The biggest leak is the roof,” predicts Boelen. “Dh”, Karin responds. The attic is now unheatable. “You can’t do anything with it.”
The house was built in a time when the Groningen natural gas was not available, even before the oil crisis. No builder was concerned about saving energy. “The heat sprays out, it’s like a bus shelter.”
It starts to blow uncomfortably in the house when Boelen turns on a large fan for a ‘blower door test’. The fan, placed in a doorway, creates a controlled draft. The house is open on all sides, revealing images that Boelen makes with an infrared camera.
The draft went past the front door, through the meter cupboard, along the connecting door to the garage, through the skylights and along the window frames. “Here,” he points at a window. “All seventies, wood on wood.” It gets cold through the seam between roof and facade, the wind whistles through the supply pipe of the central heating boiler. The old double glazing hardly insulates, the roof is almost a bare sheet under the tiles.
After the test, which lasts all morning, Boelen sits down at the dining table with grit in his hair and the first impetus for a step-by-step plan. In short: first close the cracks, with cheap materials such as draft strips and tape.
Then install ‘balanced ventilation’, a modern system that refreshes the air but hardly loses any heat.
Insulating the roof (from the inside, a curse for many builders), preferably with flax, because that breathes in the summer.
Insulating the cavity wall, all windows fitted with the best double glazing.
I ensure such a reduction in the energy demand that it becomes utter madness to drive a heating network into the ground
Boelen predicts that all these interventions will reduce the temperature of the central heating boiler in steps from 80 to 40 to 50 degrees Celsius. “Then you could switch to an electric heat pump.” Because such a pump only works with that lower water temperature. It is then often necessary to adjust the radiators.
Such a plan is not necessarily cheap. If a private person does a lot himself, it can be better than expected, but if professionals have to work, the price can easily rise to tens of thousands of euros. Installing balanced ventilation in an older home in particular is a specialist job.
On the other hand, Boelen argues that some of the interventions – such as replacing worn double glazing – actually fall under normal maintenance. And that every homeowner can start for a few hundred euros by closing cracks.
Afterwards, when he continues to talk about his work in an eatery on the highway, Boelen waves a pile of A4 sheets of reports in other houses. “Cracks, cracks, cracks”.
He and his partner Felix van Gemen call their working method the ‘Paris Proof Plan’. Based on a calculation method that they adopted from the German consultancy Passivhaus Institut, they claim that they can reduce the heat demand of houses by 50 to 70 percent. “I can halve the airtightness with two fingers in the nose. For every home in the Netherlands.”
Then people open a window to get fresh air in. Then you don’t achieve anything for your gas bill, do you?
“That is an important point if you are going to close gaps: if you do nothing further, the air quality will first deteriorate. Although I think it will not be that bad in practice with this house, because the worst leaks are in the attic.
“Now there is a lot wrong with this house. It is not comfortable in the attic, and the ventilation is not right. In the final situation, the ventilation and the energy performance of the house are correct. You start with the cracks. And if you then take that step to improve that ventilation, bam, you’re in the right place. I see the same every day. Lots of cracks that are easy to fix. And a final situation in which your own electric heat pump seems the most logical choice.”
The Netherlands Environmental Assessment Agency estimates that half of the homes will be made more sustainable with a heat pump. Half goes through a heat network. Apparently that’s the cheapest.
“But if you start working as a homeowner and you do it as well as reasonably possible, you will reach a point where you no longer need that heat network. I ensure such a reduction in the energy demand that it becomes utter madness to drive a heat network into the ground.
“Last month I was hired in Purmerend by a tenants’ association. The homes were already insulated in preparation for a high-temperature biomass heating network [circa 80°C]. The association did not trust that story, so we did a measurement. The wind continued to blow under the insulated roof. It was not airtight at all. That happens often.
“As your step-by-step plan progresses, you come to a point where you switch to something without natural gas: an electric heat pump. Which is also more comfortable, because with a heat network you cannot cool in the summer. And that heat network will not fix your ventilation and insulation either. A well-ventilated house is really nice, also for your health. COPD and asthma are closely related to a poor indoor climate.”
What do people actually want if they want to make their home more sustainable? Do they want to get rid of gas, like the Van den Bosch family?
“I see that a lot. But such people receive offers to make their house gas-free for 70,000 euros. A new shell around the facade, remove the roof and insulate from the outside. And then they say: are you completely screwed up? Our step-by-step approach also takes you to a point where the gas boiler can be removed. I notice that people find that a nice perspective for action. I can get started with my home, but I don’t have to buy a heat pump right away, I’m going to do it in steps. See how low I can set the temperature of the central heating boiler, see how my indoor climate improves.”
The insulation you prescribe is relatively modest. You choose solutions that require little equipment.
“Correct. I am very concerned about what CO2 to make the Netherlands climate neutral. That’s why I love natural materials so much. Do you know Biense Dijkstra? He makes insulating material from cattails, that is, reed cigars. That stuff works great and it’s great fun for the construction industry to work with.
“I just bought a house from the seventies myself, it is very poorly insulated. I will insulate from the inside with hemp.” The roof remains in place, because maximum insulation, with a package of 35 centimeters thickness, as the government wants, is exaggerated in his opinion. “It often doesn’t fit, so the renovation becomes very drastic. And if the roof insulation is then poorly executed and there is a wind blowing in the attic, you won’t notice it yet.”
Don’t you sweat on your back if you as a homeowner have to organize all this yourself?
“Yes. The total care provider that takes your home to a new, energy-efficient and well-ventilated situation – I don’t know them yet. You are a pioneer if you start working on your home now. But being honest about pioneering helps. The demand for house whisperers is becoming huge.”
A version of this article also appeared in NRC Handelsblad on 20 November 2021
A version of this article also appeared in NRC in the morning of November 20, 2021