I’m planning the renovation of a small Swiss single-family house from the 80s and trying to decide how far to go (bare minimum or THPE) purely from a subsidy / tax / ROI perspective.
The house is comfortable and structurally sound with internal insulation. The main weakness is electric heating. Windows are dated and will be replaced, with some openings enlarged.
Scenario B: Heating + windows
Better comfort, moderate subsidies, still relatively simple
Heat pump
Full window replacement + some enlarged openings
Scenario C: Global renovation
Highest cost, maximum subsidies, more admin and execution risk
Heat pump
Windows
Façade and roof insulation
THPE only if it improves incentives
What I’m trying to understand
Where is the best marginal return in real life?
At what point does “doing more” stop making financial sense?
Does aiming for THPE meaningfully improve the net outcome, or mainly add complexity?
How to optimise for tax + subsidies? I want to see how to best benefit from the last years where it’s possible to deduct renovation work via the rental value tax (valeur locative).
Questions for those who’ve done it
Which scenario delivered the best net result after subsidies + taxes?
Any sequencing or grouping mistakes you’d avoid in hindsight?
Better to optimise for cash subsidies now or tax deductions over time?
Thanks for any real-world feedback or lessons learned.
May I ask why something along the lines of Heat Pump + Solar is not on the cards? For us this had the best ROI (Maximize self usage of the solar with the heat pump). Do you have a lot of shade?
Often in GEAK terms, heat pump + solar can “hack” you up into the C category, which is already very good.
Only question is then will the current roof last as long as the solar (30-50 years). If not you need to replace roof surface, and then from an opportunity cost perspective it makes sense to insulate the roof as well (since they’ve already pulled off the roofing material and the scaffolding is up)
I think it depends on the specific u-wert of the existing fassade…but my assessment was that a heat pump reduces the kwh for heating by 75-80% (depending on quality of install and flow temperature), A full envelope reno would get that at best and for much more cost.
Furthermore when talking about fassade insulation, thermal bridging can become a massive problem if you have balconies or terraces not thermally disconnected from the building.
No need to take my word for it: here’s a GEAK expert saying the exact same thing in a UBS article:
“If an existing building is fully renovated, for example, by replacing the windows and renovating the roof, including installing a photovoltaic system and switching to a heat pump, it will no doubt be rated class C”
“However, when it comes to facade insulation, I don’t see much changing for the better at the moment. The state would need to improve the general framework first.”
I interpret this as an acknowledgement that from an ROI perspective a fassade insulation doesn’t add up…
There is of course one caveat to my argument, and that is if the current building shell is so inefficient that you can’t get a heat pump in with a sufficiently low flow temp. Then you need to start with “envelope first”. Also be careful with heat pump sizing, needs to take account of end state heating load or it will kill the compressor <5years
I considered heat + solar as some solar is necessary, but it seems that since November 25, a new law recommends/forces to use all the reasonably available surface for solar panels. So this is now quite an extra cost, which even begs the question of why not use solar tiles to not pay the roofing + the solar panels…
The current roof doesn’t seem in a shape that it’ll last another 30-40 years so I’m weary of installing a solar system knowing that some tiles might break below and that the thermic enveloppe would not be optimised either. It somehow feels like a bandaid on a bigger problem to me that I’ll have to pay for further down the road, and perhaps at a time where subsidies won’t exist anymore…
I’m waiting on some expertises to get a better picture of the state of the roof, and am also looking for someone to do the cecb+ diagnostic ASAP to help me plan the project better as it impacts quite a bit the final look and feel of the house as well as how we balance expenses
Working on the facade + roof ensures the best thermic insulation and the minimum amount of energy needed to keep the house warm. While it’s technically the best option, it’s also the most expensive one. What I’m not quite sure of atm is how big of an extra expense it becomes in relative terms including the tax cuts + subsidies. So that’s what I’m trying to figure out atm.
I was also thinking of doing it the way @Ardius did splitting the work over 2 years. If I understand well, you only installed the solar panels in the 2nd year? did you do anything else? and why did you choose not change the heating system? I’m still waiting on my first electric bill, but previous tenants paid 1k+ per months on electricity only…
@Stingy_cnt, thank you for the article, I wasn’t aware of the discount in mortgage rate as well!
Splitting renovation between allow you to pay less taxes. For example, 20k per year is better than 40k in one single year.
Where do you live ?
I keep the electric heating system as i dont want to install a full hydraulic heating system. This is very expensive. Heat pump is one thing, but you have to create a full hydraulic system in your house.
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