Hello everyone,
so far, I have been an advocate for a ventilation system with heat recovery (decentralized in the new build – a central system is too expensive for us in terms of purchase and maintenance).
Our general contractor (GC) is planning a simple exhaust ventilation system from Lunos. I had asked him to obtain quotes from two companies (Lunos and Seventilation) for a ventilation system with heat recovery. The price difference would be between 3,000 and 4,000 euros.
On Saturday, we had another discussion with the planning engineer from our GC.
He raised the question of how much savings a heat recovery system would actually provide and when it would likely pay off.
The geothermal heating system (after a startup phase of about 1 year with higher costs) is expected to have an annual electricity consumption of around 600 euros (I am cautiously estimating 700 euros).
The ventilation system is supposed to recover and return 80-90% of the waste heat (the airflow direction changes every 75 seconds). I don’t believe, for example, that this could save as much as 50% of the electricity costs for the geothermal system.
If around 100 euros are saved per year, the ventilation system with heat recovery would take about 30 years to pay off at current electricity prices (assuming everything lasts and no additional costs arise).
This does not yet include the electricity consumption of the ventilation system itself or possible regular additional maintenance.
On the other hand, I am not under the illusion that electricity prices will remain the same.
What are your thoughts on this?
f-pNo
so far, I have been an advocate for a ventilation system with heat recovery (decentralized in the new build – a central system is too expensive for us in terms of purchase and maintenance).
Our general contractor (GC) is planning a simple exhaust ventilation system from Lunos. I had asked him to obtain quotes from two companies (Lunos and Seventilation) for a ventilation system with heat recovery. The price difference would be between 3,000 and 4,000 euros.
On Saturday, we had another discussion with the planning engineer from our GC.
He raised the question of how much savings a heat recovery system would actually provide and when it would likely pay off.
The geothermal heating system (after a startup phase of about 1 year with higher costs) is expected to have an annual electricity consumption of around 600 euros (I am cautiously estimating 700 euros).
The ventilation system is supposed to recover and return 80-90% of the waste heat (the airflow direction changes every 75 seconds). I don’t believe, for example, that this could save as much as 50% of the electricity costs for the geothermal system.
If around 100 euros are saved per year, the ventilation system with heat recovery would take about 30 years to pay off at current electricity prices (assuming everything lasts and no additional costs arise).
This does not yet include the electricity consumption of the ventilation system itself or possible regular additional maintenance.
On the other hand, I am not under the illusion that electricity prices will remain the same.
What are your thoughts on this?
f-pNo
B
Bauexperte29 Jul 2013 14:23Hello,
**Central exhaust ventilation systems with decentralized outdoor air supply are technically simpler because they only require an exhaust air duct system, but no supply air ducts. Outdoor air enters through several wall vents. However, these systems have a significant drawback: the outdoor air arrives cold and unheated in the rooms during winter, and the air delivery per room strongly depends on wind pressure.
Both decentralized and central exhaust ventilation systems expel the used air along with its heat from the house. The heating system then has to warm up the incoming cold outdoor air in each room from outside temperature to room temperature. This consumes energy. Compared to window ventilation, a pure exhaust system does not save energy but only offers the comfort of automatic moisture removal, fresh air supply, and better controllability. On the other hand, if you install a central supply and exhaust ventilation system with ducts for both supply and exhaust air, these ducts can be combined in a supply-exhaust heat exchanger to preheat the cold outdoor air using the heat from the exhaust air – this is also possible with decentralized ventilation systems.
Modern supply and exhaust ventilation systems with heat recovery (HRV) can recover up to 94 percent of the heat from the exhaust air. With them, the cold outdoor air can be preheated to, for example, around 17°C (63°F) in winter without additional heating energy.
*** For health and economic reasons, controlled ventilation cannot be dispensed with in new buildings.
This involves the combination of cost-effective thermal insulation measures with heat recovery from the mechanical ventilation system. The market offers a wide variety of ventilation units that differ in design and performance data. Prospective buyers and planners depend on manufacturer-neutral technical information about comparable individual units. Gathering this information can be quite laborious. Furthermore, a mere product description is often not sufficient. A neutral test report that allows direct comparison with other devices is very helpful in selecting a suitable unit.
A prerequisite for choosing the right device is the development of a meaningful ventilation concept.
Additionally – from my humble point of view, there are only two choices when selecting a ventilation system, which in my opinion should definitely not be considered from a purely payback perspective, because they don’t and in my opinion shouldn’t have to. Mold in new buildings is something that cannot be controlled with conventional window ventilation – especially not with trickle vents. Current and certainly future energy-saving regulations require increasingly airtight buildings; the sense and purpose of this is debatable, but this trend is irreversible. Builders who want to benefit from government loans such as those from KfW (or similar funding bodies) are forced to build increasingly airtight. With this airtight building envelope, they accept adverse side effects that must in turn be addressed with even more technical solutions. Here, there are decentralized and central ventilation systems; every smart homeowner should choose one of these options – always with heat recovery – depending on their budget.
From my experience, both partners of a building household nowadays (whether married or cohabiting) usually work and are unable to ensure the ventilation needs of the house for the first couple of years after construction. Although the blocks are mostly adhered with adhesive today, a lot of water still enters the house through the screed that must evaporate and be vented out – and keen, “internet-educated” homeowners want to move in right after signing the contract. The later residents also produce about 4 liters (1 gallon) of water per person per day that is released into the atmosphere of the single-family home. This is even more critical in detached houses where the so-called "plastic foil" limits water escape.
A decentralized ventilation system with heat recovery costs around EUR 5,000 for an average single-family house, including the ventilation concept. This well-invested money saves trouble with mold and prevents stale odors in the house. The same applies to central systems, but the costs for these are around EUR 13,000 to 15,000 and not affordable for every homeowner.
Sources:** Federal Association of Energy Consumers
*** TZWL e.V. – European Test Center for Residential Ventilation Devices e.V.
Best regards, Bauexperte
f-pNo schrieb:Is your planning engineer employed by your provider’s company, or were they brought in externally?
Our house will have geothermal heating with underfloor heating. It is being built with Ytong blocks without additional insulation. Additionally, our construction company wants to install a exhaust ventilation system from Lunos. Moist air is extracted from the wet rooms (bathrooms, kitchen, utility room). According to the description, the resulting negative pressure draws fresh air into the living areas through ventilation slots. This would ensure sufficient air exchange and removal of any humidity.
According to the plan, the geothermal heating system in this setup is expected to have electricity costs of about 600 euros per year after the first year.
Personally – just from a feeling – I would prefer to convert this to a decentralized ventilation system with heat recovery. However, our planning engineer questioned when and if the higher costs (3,000 – 4,000 euros) would pay off.
**Central exhaust ventilation systems with decentralized outdoor air supply are technically simpler because they only require an exhaust air duct system, but no supply air ducts. Outdoor air enters through several wall vents. However, these systems have a significant drawback: the outdoor air arrives cold and unheated in the rooms during winter, and the air delivery per room strongly depends on wind pressure.
Both decentralized and central exhaust ventilation systems expel the used air along with its heat from the house. The heating system then has to warm up the incoming cold outdoor air in each room from outside temperature to room temperature. This consumes energy. Compared to window ventilation, a pure exhaust system does not save energy but only offers the comfort of automatic moisture removal, fresh air supply, and better controllability. On the other hand, if you install a central supply and exhaust ventilation system with ducts for both supply and exhaust air, these ducts can be combined in a supply-exhaust heat exchanger to preheat the cold outdoor air using the heat from the exhaust air – this is also possible with decentralized ventilation systems.
Modern supply and exhaust ventilation systems with heat recovery (HRV) can recover up to 94 percent of the heat from the exhaust air. With them, the cold outdoor air can be preheated to, for example, around 17°C (63°F) in winter without additional heating energy.
*** For health and economic reasons, controlled ventilation cannot be dispensed with in new buildings.
This involves the combination of cost-effective thermal insulation measures with heat recovery from the mechanical ventilation system. The market offers a wide variety of ventilation units that differ in design and performance data. Prospective buyers and planners depend on manufacturer-neutral technical information about comparable individual units. Gathering this information can be quite laborious. Furthermore, a mere product description is often not sufficient. A neutral test report that allows direct comparison with other devices is very helpful in selecting a suitable unit.
A prerequisite for choosing the right device is the development of a meaningful ventilation concept.
f-pNo schrieb:Even in the 21st century, we can only really protect ourselves from the cold, not effectively from heat. This issue can only be somewhat managed by building thicker masonry, consistently avoiding windows on the south side, or at least shading them constantly during sunny periods with shading devices. Everything else is wishful thinking or requires the use of air conditioning units; by the way, a system that also uses the underfloor heating for "cooling" is not worth it, because you will hardly notice a 2°C (3.6°F) difference... except in the construction costs.
No matter how you look at it – over time the house heats up.
f-pNo schrieb:See above.
Can you give me other arguments IN FAVOR of a decentralized ventilation system with heat recovery?
Additionally – from my humble point of view, there are only two choices when selecting a ventilation system, which in my opinion should definitely not be considered from a purely payback perspective, because they don’t and in my opinion shouldn’t have to. Mold in new buildings is something that cannot be controlled with conventional window ventilation – especially not with trickle vents. Current and certainly future energy-saving regulations require increasingly airtight buildings; the sense and purpose of this is debatable, but this trend is irreversible. Builders who want to benefit from government loans such as those from KfW (or similar funding bodies) are forced to build increasingly airtight. With this airtight building envelope, they accept adverse side effects that must in turn be addressed with even more technical solutions. Here, there are decentralized and central ventilation systems; every smart homeowner should choose one of these options – always with heat recovery – depending on their budget.
From my experience, both partners of a building household nowadays (whether married or cohabiting) usually work and are unable to ensure the ventilation needs of the house for the first couple of years after construction. Although the blocks are mostly adhered with adhesive today, a lot of water still enters the house through the screed that must evaporate and be vented out – and keen, “internet-educated” homeowners want to move in right after signing the contract. The later residents also produce about 4 liters (1 gallon) of water per person per day that is released into the atmosphere of the single-family home. This is even more critical in detached houses where the so-called "plastic foil" limits water escape.
A decentralized ventilation system with heat recovery costs around EUR 5,000 for an average single-family house, including the ventilation concept. This well-invested money saves trouble with mold and prevents stale odors in the house. The same applies to central systems, but the costs for these are around EUR 13,000 to 15,000 and not affordable for every homeowner.
Sources:** Federal Association of Energy Consumers
*** TZWL e.V. – European Test Center for Residential Ventilation Devices e.V.
Best regards, Bauexperte
P
perlenmann29 Jul 2013 16:47@Bauexperte and Admin: Something is definitely wrong here. I can navigate the forum just fine with Firefox, but my post was deleted. That’s frustrating. I haven’t had problems like this in any other forum.
Now, back to the topic:
Pro: Soundproofing (How should that be done with decentralized ventilation?)
You’ve already identified the pollen filter yourself.
Ever opened the bathroom window slightly in winter, just a little draft with -10°C (14°F) cold air? Then you know what it means when the incoming air is heated.
In terms of cost, the additional expenses probably won’t pay off, but it is a gain in comfort.
Also, a heat exchanger can cool the warm air coming from outside if it’s cooler inside the house. However, in hot weather the ventilation is usually set to minimum, with stronger ventilation at night.
Now, back to the topic:
Pro: Soundproofing (How should that be done with decentralized ventilation?)
You’ve already identified the pollen filter yourself.
Ever opened the bathroom window slightly in winter, just a little draft with -10°C (14°F) cold air? Then you know what it means when the incoming air is heated.
In terms of cost, the additional expenses probably won’t pay off, but it is a gain in comfort.
Also, a heat exchanger can cool the warm air coming from outside if it’s cooler inside the house. However, in hot weather the ventilation is usually set to minimum, with stronger ventilation at night.
Hello Building Expert,
According to DIN 1946-6, natural window ventilation is also an accepted ventilation measure (LtM).
The business based on fear of mold, however, generates good revenue. General contractors and construction managers make frequent use of this.
Best regards.
Building Expert schrieb:Such a general statement is incorrect. I have supervised numerous building projects under the conditions of the 2009 Energy Saving Ordinance without ventilation systems. To this day, there has been no sign of mold!
...For health and economic reasons, controlled ventilation cannot be omitted in new buildings...
Building Expert schrieb:Correct, but unfortunately the basics often fail already at this stage.
...A prerequisite for selecting the appropriate device is the development of a sensible ventilation concept.
Building Expert schrieb:I see it differently. With proper building construction (passive summer heat protection), a period of summer heat can be endured well without using mechanical cooling.
...We can only protect ourselves from cold in the 21st century, but not effectively from heat.
Building Expert schrieb:Only a cynic would suspect something malicious here.
...With this airtightness of the building envelope, you introduce negative side effects that have to be countered with even more technology.
Building Expert schrieb:To remove temporary construction moisture, no long-term ventilation system is necessary.
...From my experience, nowadays both partners in a building community (whether married or cohabiting) are employed and not in a position to ensure the ventilation requirements of the house within the first two years.
According to DIN 1946-6, natural window ventilation is also an accepted ventilation measure (LtM).
The business based on fear of mold, however, generates good revenue. General contractors and construction managers make frequent use of this.
Best regards.
B
Bauexperte30 Jul 2013 13:03Hello €uro,
There have been and will always be exceptions. I’m not saying this out of thin air; it reflects my experience over recent years. Of course, it can work without ventilation, but as you know, this also leads to additional costs.
I haven’t denied that and have already mentioned how it can be done
I haven’t suspected that for a long time...
I know, but that doesn’t make it any better.
You’re much better at spreading fear than I am
Regards, Bauexperte
€uro schrieb:
Such a general statement is incorrect. I have supervised enough construction projects under the framework conditions of the 2009 Energy Saving Ordinance without ventilation systems. To this day, no sign of mold!
There have been and will always be exceptions. I’m not saying this out of thin air; it reflects my experience over recent years. Of course, it can work without ventilation, but as you know, this also leads to additional costs.
€uro schrieb:
I see it differently. With sensible building construction (passive summer heat protection), a summer heatwave can be endured well even without technical cooling.
I haven’t denied that and have already mentioned how it can be done
€uro schrieb:
Only a scoundrel would suspect ill intent here
I haven’t suspected that for a long time...
€uro schrieb:
According to DIN 1946-6, window ventilation is also recognized as an approved ventilation measure (LtM).
I know, but that doesn’t make it any better.
€uro schrieb:
The business built on fear of mold certainly generates good sales. General contractors especially make frequent use of this
You’re much better at spreading fear than I am
Regards, Bauexperte
B
Bauexperte30 Jul 2013 13:05Hello Perlenmann,
The current version of Firefox is problematic, and unfortunately, there’s nothing that can be done about it. In any case, your post was not deleted by either the admin or me.
Regards, Bauexperte
Perlenmann schrieb:
@Bauexperte and Admin: Something is really wrong here. I can browse the forum normally with Firefox, but my post was deleted. That’s annoying. I don’t have issues like this in any other forum.
The current version of Firefox is problematic, and unfortunately, there’s nothing that can be done about it. In any case, your post was not deleted by either the admin or me.
Regards, Bauexperte
There have always been exceptions and there always will be. I’m not writing this from thin air; it reflects my experience over the past few years. Of course, it is possible to build without ventilation systems, but as you know, that also leads to additional costs.I’m a bit provocative when I ask whether your experiences might be related to the fact that you primarily build with aerated concrete? I’ve often heard that aerated concrete retains more moisture during the construction phase and doesn’t dry out as quickly. Therefore, the requirements for the occupants’ ventilation behavior are stricter, especially during the first 1-2 years...
Regarding pre-warmed supply air: even window frame vents provide some degree of warming... During measurements at an outside temperature of -5°C (23°F), the supply air entering the room was already warmed up to 8°C (46°F)... Although this is not on the level of a mechanical ventilation system with heat recovery, it is significantly more than most probably expected.
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