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Comment by brnt | Hacker News Reader

For an A+++ energy rated house, you can't have holes in walls where I live. That means you can't have cooker extractors that extract, you can only have them run the air through a filter. But this is really silly, because a major 'exhaust' is water vapor, which filters don't help with. A more humid house is bad for many reasons, and often results in people opening windows anyway. Yes, an A+++ house also requires air refreshing with energy recovery, but it takes ages to get that sort of humidity out that way. Running an airco just for dehumidification is also expensive.

It's short sighted imho. The extractor is precisely the right place to just move air out for all kinds of health reasons, maybe someone should work on one that recaptures some of the heat (that would also make sense!); I have not yet seen one.

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> For an A+++ energy rated house, you can't have holes in walls where I live. That means you can't have cooker extractors that extract, you can only have them run the air through a filter.

It's possible to install dampers that are normally closed for airtightness, but open when the kitchen vent is activated (both on the exhaust, and makeup air, side of things):

* https://www.greenbuildingadvisor.com/article/makeup-air-for-...

Even the Passive House folks are fine with this arrangement (§3.4):

> When the exhaust air system is not operating the exhaust air and intake air vents should close airtight and should not cause any leakage volume flow. Furthermore, additional insulation will be advantageous at these locations.

* https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

So I'm not sure why your building codes mandate recirculation, since I'm guessing even they wouldn't be as "strict" as the PH folks.

In general theres two kinds of ways to meet code: by design or by test. They might be referring to a 'design' stipulation which wouldn't require a real test. If they choose to be tested instead, then the 'open when activated' would likely pass.

EDIT: it looks like the terms are 'Prescriptive' and 'Performance'. e.g. https://www.energycodes.gov/sites/default/files/2019-09/Ener...

Berbel has a unit that opens when using the unit and closes, when not in use. Quite ingenious, if you ask me.

[1]: https://www.berbel.de/dunstabzuege/zubehoer/abluft-zubehoer/...

That's clever, but this [1] is already common and I guess not much worse?

[1] https://www.ventilatieshop.com/terugslagklep-in-ventilatieka...

It is much worse. The Berbel retains the insulation provided by the wall, when closed. This is nothing more than a fancy hole in the wall.

Opening and closing, means you get the best of both worlds.

there are a lot of available ventilation solutions that recover the energy and cycle air in your use. they start at 200€ a unit and go up from there.

i think the modern cooking extractors are all built into the countertops and just filter the air. at least thats the trend in germany

The point is that those systems do not integrate with extractors, and filtering only removed VOCs and particulates, not water vapour, which you would prefer to extract as well.

Heat recovery from an extractor (eg remove heat from air before expelling) would achieve the goal the rating is aimed at, without compromising indoor air quality by not having a way to remove humidity. Or maybe another kind of integrated dehumidifier that discharges in your sink/plumbing maybe.

Those filter-only extractors won't do for anyone serious about indoor air quality.

yeah but in my opinion in modern homes this is automated and regulated house-wide with the mentioned air circulators that recover the energy. they also expell humidity afaik

You'll still have to accept an hour or so of elevated humidity. I prefer not to.

Can you just settle for a measly A++? Is there an A++++ rating? Seems like a silly system anyway.

Assuming you're joking about the ++'s on the end, the reality is that the efficiency scales (like the appliance energy efficiency scales in europe) were designed when what was considered "good", was vastly different to what it is now.

The choice is to either rebalance/demote everyone who built a top rated property 25 years ago, or add more tiers. Political will means we do the latter.

Why can't we just use numbers? "This house in this climate will use about X kwh per year for heating/cooling". That's what appliances do. No messing with scales and tiers and having to constantly re-balance.

It's also more directly meaningful to customers. An A+++++ mansion is going to use more energy to heat than a modest A+++ house.

> Why can't we just use numbers?

Because numbers require everyone who is involved in comparing options (i.e. consudmers) to have intimate knowledge of what those numbers mean. Is X kwh actually good? How does it compare to other houses in the area? What number do you use - the amount of energy it will take to heat the house, or the amount of energy of a specific type you will use. How do you compare those (a house with Natural Gas as a heat source will require significantly less electricity to heat than a house with electric radiators, but will likely _cost_ more).

Using ratings gives a standardised way to compare them. If you compare two houses, one has an A rating and one has a B rating, the B one is strictly worse, by an amount that someone who knows something about this has deemed significant.

> That's what appliances do

Appliances are graded on a similar score here. Every appliance you buy in the EU has one of these [0] labels (which has the same problem).

> An A+++++ mansion is going to use more energy to heat than a modest A+++ house.

You're comparing two different things here, and forgetting a very important point - someone who is going to buy a "mansion" is not going to buy a modest house, so it doesn't matter what the rating of the house is in comparison. What matters is the rating of the mansion next door.

[0] https://en.wikipedia.org/wiki/European_Union_energy_label

Hm, in the US we have energy labels on appliances like [1] that just tells you how much energy it will likely use. When shopping for a fridge, you can directly compare different models.

It even shows the average cost of other similar products. So you can see both the absolute numbers and a visual representation of how efficient something is in relative terms without having to squint and count '+' marks.

I don't see why we couldn't do that for houses. Maybe use a unit like BTU instead of kwh to account for different heating sources. And include a comparison to the average range for houses in the area.

This would be a lot more concrete and avoid arbitrary ratings. If the ratings are based on bureaucratic rules (i.e. can't have stovetop vents) instead of actual measurements, then it feels a lot less meaningful. "This house will cost about $X to heat each year" is a much more useful piece of information for someone house shopping.

[1] https://www.sce.com/residential/home-energy-guide/energy-sta...

We can, don't have them on hand though. There's still a huge number of houses with B or lower ratings, so I only if you're looking at new builds do you have to count plusses ;)

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