I don't understand why we don't mandate stricter energy efficiency for new buildings. Why is it still legal to rely on fossil fuels for heating for example?
Remember it's the energy TCO (total cost of ownership over project lifetime) that captures the full environmental impact of the house, as every MJ of energy - regardless if embodied or operating - translates into a known quantity of GHG emmissions, particle pollution, and so on.
In a pleasant surprise, spending energy later (in energy costs, rather than embodied) is better than spending it today for the environment! Energy produced in the future will surely emmit less GHG and pollution than today (better techniques!), and the GHG will dwell less time in the athmosphere, so less compounding effects on the total temperature rise that we'll have at the end of this century.
If you care about the environment, you have to consider the energy TCO.
https://ec.europa.eu/energy/en/topics/energy-efficiency/ener...
The actual implementation is left up to individual countries. In my country, Lithuania, it means from 2021 all new houses require insulation to be at the same level as Passivhaus, and buildings to obtain the majority of their energy from renewable sources (so most new houses will have PV installed). It gets cold here in the winter (-20c isn't uncommon), so if it can work here, it can work pretty much anywhere in Europe.
As can be expected this will push the price of new builds up, but the benefits are a more comfortable and healthy environment (I grew up in drafty & moldy houses in the UK) and lower energy costs (grid-tied PV installations, without a battery, usually pay back in 7 to 10 years, after which they provide free energy for the life of the system).
Edit: I should mention the prices will not rise in a significant way. Materials for the structure/building envelope are usually a small part of construction costs, and those required for Passivehaus are not expensive or hard to obtain. Of course propery developers will complain, as the extra cost will come out of their profit margin :-)
I have a friend who is a building a house by himself. I think that's really cool. If you set standards too high that wont be possible.
Finally bureaucracy sucks. Even an "obvious" regulation that all houses follows like "your house has to have a roof" has the potential to become seriously annoying if you have to get an inspector who is only available in a month and only on Mondays 9-10, to take a look and write a statement that your house indeed does have a roof.
Apparently "14% of UK greenhouse gases come from our homes, a similar level to emissions from cars. In major cities gas boilers are also a main source of nitrogen dioxide emissions."[1]
The standard is still storage headers and other wall mounted electrical heaters. I remember those from childhood, and how happy we were to switch to gas-fired central heating.
There are electric boilers which can power a hot-water based heating system; they are substantially more expensive to operate than current gas boilers (due to the UK price differential between gas and electricity).
My most favoured approach is an air source heat pump, and larger radiators/underfloor heating to make use of the lower temperature heat source. More expensive to install and run than a gas fired central heating system.
Perhaps in the house after next, this will be standard - or I might even be able to buy a Passivhaus.
Underfloor electrical heating is apparently a lot more efficient than radiators, e.g. because you only need to run them at a much lower temperature. If you combine with things like ground source heat pumps and solar panels, the electric heating proposition looks a lot more appealing.
That said, the conclusion I came to is that for an old place that doesn't otherwise need major work, it just isn't worth the expense of making the switch. It might be that if I were to move somewhere that needed a complete refurbishment anyway, then I would. Even then, with most homes, at least in cities like London, being flats rather than houses, then things like solar panels and heat pumps become much more difficult if not impossible to arrange.
[0] https://www.designingbuildings.co.uk/wiki/English_housing_st...
[1] https://en.wikipedia.org/wiki/Prefabs_in_the_United_Kingdom
[2] https://www.theguardian.com/society/2009/mar/17/historic-pre...
https://ww2.energy.ca.gov/title24/2019standards/documents/20...
https://www.vox.com/energy-and-environment/2019/5/31/1864690...
Like applying the Toyota Production System to A/E/C.
Better improvement at a faster rate, without the inevitable recurring food fights (lawsuits).
> Why is it still legal to rely on fossil fuels for heating for example?
Because there are few alternatives. You can use wood, but that comes with its own problems.