ᐅ Mechanical ventilation with heat recovery instead of solar thermal energy?

Dr Hix schrieb:
A photovoltaic system has no impact on the primary energy demand at all. You probably mean solar thermal.
I would suggest having the calculations done in advance instead of blindly trusting the architect. In my opinion, it should definitely be possible if you invest a bit more in insulation as well. This results in a much more reasonable overall package, as solar thermal often does not pay off and, unlike mechanical ventilation with heat recovery, offers no additional benefits.

I would like to share our conclusion:



Since the 2016 Energy Saving Ordinance, gas with mechanical ventilation with heat recovery without solar thermal is NO LONGER an acceptable substitute measure under the Renewable Energy Heat Act.

Our energy consultant calculated all of this for us, and I think many here in the forum do not fully understand the Renewable Energy Heat Act.


We comply with the Energy Saving Ordinance using gas + solar + mechanical ventilation with heat recovery, but even then we do not achieve a primary energy demand 15% below what the Energy Saving Ordinance requires.

To put it bluntly, you would need about 50cm (20 inches) more insulation and windows with a total U-value of 0.3 to reduce the primary energy demand by 15% below the Energy Saving Ordinance if you want to use gas with mechanical ventilation but no solar thermal.


I would argue that not all energy consultants and not everyone here has read the Renewable Energy Heat Act, and in the end, some just say it is allowed because the Energy Saving Ordinance is met according to the thermal protection certificate. But it simply isn’t.

Because to comply with ONLY the Energy Saving Ordinance, gas + mechanical ventilation with heat recovery + slightly more insulation might be enough.

But to be accepted as a substitute measure for omitting solar thermal, a primary energy demand 15% below the 2016 Energy Saving Ordinance standard is required; I can gladly share the legal text again.


Those who built according to the 2016 Energy Saving Ordinance using gas and mechanical ventilation without solar thermal are welcome to share their complete thermal protection certificate—I am very curious to see their calculations.


This might have been possible under the 2014 Energy Saving Ordinance, but no longer with the stricter 2016 version.


If your energy consultant has explicitly given you written confirmation to the contrary, then the responsibility lies with them, and since these matters are rarely checked, you have luckily saved a few dollars.

Aliban2014 schrieb:
Our energy consultant ran all the numbers for us

I don’t want to claim that this always works with gas and mechanical ventilation with heat recovery. However, there are certainly more factors involved than just the so-called Renewable Energy Heat Act. In your case, it’s probably the geothermal regulation in Baden-Württemberg that pushed you towards solar thermal.

When an energy consultant performs calculations, there are many adjustable parameters that often remain unused due to convenience or lack of knowledge, or because the software being used cannot represent them. And of course, every building examined is unique in itself.

I tend to agree. Condensing gas boilers and decentralized controlled mechanical ventilation are the two main components many construction companies in this region use for energy-efficient standard houses according to the energy saving ordinance, without solar panels. Our construction company alone builds about 400 of these energy saving ordinance houses per year. Especially with the tightening of the energy saving ordinance in 2016, the system was switched from solar to decentralized controlled mechanical ventilation. This change was certainly not made on a whim or without proper evaluation.

Dr Hix schrieb:


1)
In your case, the geothermal law in Baden-Württemberg probably also forced you towards solar thermal.

2)
When calculations are done by the energy consultant, there are many adjusting factors that are often not used due to convenience or lack of knowledge, or cannot be represented by the software used. And of course, each building considered is unique.

Regarding 1)
No, because the Renewable Energies Heat Act in Baden-Württemberg applies only to renovations and NOT to new buildings. It would have been great for us, because then we could have installed photovoltaic systems instead of solar thermal. That would have been accepted as a compensatory measure. The law text can be found online.

Regarding 2)
All the so-called adjusting factors were applied; it simply isn’t sufficient anymore since the 2016 Energy Saving Ordinance tightened the allowable primary energy demand so much that it can no longer be easily achieved with gas and controlled ventilation. And then, without solar, 15% less primary energy is required to qualify as a compensatory measure under the Renewable Energies Heat Act—never ever. I am still waiting for the calculations to prove this, not hearsay or verbal statements, but complete anonymized thermal insulation certificates.

In simplified terms, it’s no longer possible without 50cm (20 inches) of insulation and windows with a total U-value of 0.3 W/(m²·K) (R-value of about 1.9 ft²·°F·h/Btu), regardless of the building type.

Just post your complete anonymized thermal insulation certificate according to the 2016 Energy Saving Ordinance.

@ares83:
That’s not the point—the TWO requirements must be met and are checked separately:

1. Energy Saving Ordinance
2. Renewable Energies Heat Act

Regarding 1: The Energy Saving Ordinance and thus the annual primary energy demand can possibly be met with gas, controlled ventilation, and better insulation, under some circumstances.

Regarding 2:
Without solar, renewable energies are missing—so controlled ventilation acts as a compensatory measure. This would require the annual primary energy demand to be 15% BELOW the current 2016 Energy Saving Ordinance standard. However, because the Energy Saving Ordinance 2016 already demands a 20% reduction in primary energy demand, this cannot be achieved anymore. You would have to achieve an annual primary energy demand that is 15% lower than the already tightened 20% reduction target by using just the building shell and controlled ventilation.

It is possible to comply with the Energy Saving Ordinance while violating the Renewable Energies Heat Act, but nobody probably monitors that. This is probably why it is still done.

The contact details of the contractor’s thermal protection calculator would definitely interest many home builders.

Unfortunately, nobody here posts an anonymized thermal insulation certificate according to the 2016 Energy Saving Ordinance so that this can be checked.

Anyone who foregoes solar should be thankful for their energy consultant and remember to hold them liable if necessary.

Aliban2014 schrieb:
No, because the Renewable Energy Heat Act BW only applies to renovations and NOT to new builds

You’re right.

Aliban2014 schrieb:
all the so-called adjustment options were implemented

I find that interesting—you didn’t even ask what exactly I was referring to. But that fits with your request that someone prove you wrong by posting an energy performance certificate. Why don’t you post yours here so we can confirm that your energy consultant has indeed explored all possible options?

Aliban2014 schrieb:

Unfortunately, nobody is posting an anonymized energy performance certificate according to the 2016 Energy Saving Ordinance here, so it cannot be reviewed.

Ours wouldn’t help much here. We built to KfW 55 standard with an air-to-water heat pump and centralized mechanical ventilation with heat recovery. You can take a look, for example, on the websites of Ernst and Ernst or Tönjes and Meichsner to see how they handle these calculations.