ᐅ Challenges for MEP planners: underfloor heating flow temperature and wastewater ventilation
Created on: 15 Jul 2022 10:22
P
Pacmansh
Hello,
we are at the beginning of the construction phase for our development project with the builder, and I am having some disagreements with the MEP planner. To be better prepared for the discussion, I would appreciate your assessment.
Point 1) Supply temperature of underfloor heating, new building, KfW55 standard, air-to-water heat pump
The supply temperature of the underfloor heating (end-terrace house on both floors) was stated to me as 40°C (104°F) after inquiry. This seems absurdly high to me. Additionally, I was informed that the surface temperature is designed to a maximum of 27°C (81°F) due to the flooring materials. Somehow, this does not seem consistent. When I asked about lowering the supply temperature, the response was: "A general reduction is not feasible with the underfloor heating without reducing the pipe spacing to an unacceptable level."
Do you have any ideas how I can respond to this in a reasonably professional way? Are there any documents or sources I could refer to, or information I should request?
Point 2) Wastewater venting
Contrary to earlier agreements, this has been planned in a rather unfavorable location. The reason given is "because the wastewater vent and the residential ventilation (exhaust air) must be routed over the roof with a certain separation according to flat roof guidelines." What distance should be maintained here? A quick online search only showed a 30cm (12 inches) distance to other building components. Basically, this is about the roof penetrations and their distance from each other, correct?
we are at the beginning of the construction phase for our development project with the builder, and I am having some disagreements with the MEP planner. To be better prepared for the discussion, I would appreciate your assessment.
Point 1) Supply temperature of underfloor heating, new building, KfW55 standard, air-to-water heat pump
The supply temperature of the underfloor heating (end-terrace house on both floors) was stated to me as 40°C (104°F) after inquiry. This seems absurdly high to me. Additionally, I was informed that the surface temperature is designed to a maximum of 27°C (81°F) due to the flooring materials. Somehow, this does not seem consistent. When I asked about lowering the supply temperature, the response was: "A general reduction is not feasible with the underfloor heating without reducing the pipe spacing to an unacceptable level."
Do you have any ideas how I can respond to this in a reasonably professional way? Are there any documents or sources I could refer to, or information I should request?
Point 2) Wastewater venting
Contrary to earlier agreements, this has been planned in a rather unfavorable location. The reason given is "because the wastewater vent and the residential ventilation (exhaust air) must be routed over the roof with a certain separation according to flat roof guidelines." What distance should be maintained here? A quick online search only showed a 30cm (12 inches) distance to other building components. Basically, this is about the roof penetrations and their distance from each other, correct?
face26 schrieb:
10% won't make a big difference afterwards.Thanks! You’re probably right. I enjoy dealing with these topics and want to get the best possible result. However, I’m not the builder but the buyer, and the planners are those of the developer, so the 90% simply represent the optimum in this case.Regarding the heating circuit valves (HKV), that’s a good approach, but it’s no longer possible for us. The valves are located once in the dressing room and once in the hallway under the stairs. There is no need for heat there, so you’re absolutely right. Maybe this helps someone else who comes across the thread. Thanks for the hint.
The inspector (who also came yesterday) also pointed out the insulation of the supply and return pipes. Currently, there is aluminum-laminated mineral wool (in the pipe chases and wall cavities) and PE foam (in the screed).
It is surprising that the market has not yet corrected such a performance.
But congratulations to you! Through persistence, research, and learning about an unfamiliar subject, you have managed to achieve the best possible outcome given the circumstances. Not everyone can do this, not everyone wants to, and then they have to face the consequences during later use.
But congratulations to you! Through persistence, research, and learning about an unfamiliar subject, you have managed to achieve the best possible outcome given the circumstances. Not everyone can do this, not everyone wants to, and then they have to face the consequences during later use.
Wow. Your persistence is impressive!
It’s really shocking what companies can get away with. I think if construction slows down, these "low performers" will gradually run into trouble. Then a developer won’t be indifferent to how satisfied or dissatisfied buyers are, especially if there aren’t a hundred more lined up right away.
The problem still lies in the lack of transparency caused by specially created project companies. Buyers often don’t know which projects were actually carried out by the same company in the end.
It’s really shocking what companies can get away with. I think if construction slows down, these "low performers" will gradually run into trouble. Then a developer won’t be indifferent to how satisfied or dissatisfied buyers are, especially if there aren’t a hundred more lined up right away.
The problem still lies in the lack of transparency caused by specially created project companies. Buyers often don’t know which projects were actually carried out by the same company in the end.
Thank you all for your support. You sometimes feel a bit like a nitpicker, but it’s just that there’s so much money involved overall. Without forums like this, a layperson would be pretty much lost. This is really great.
Luckily, our developer is basically a two-person company. So you can actually reach the people responsible. That’s much more difficult with a large developer, of course. I hope the client is slowly realizing the kind of performance the MEP (mechanical, electrical, plumbing) designer is delivering here. Still, it’s probably a good business for him. There are a total of 15 housing units; he has a lot of trouble with me, but he makes a high margin with the others.
Luckily, our developer is basically a two-person company. So you can actually reach the people responsible. That’s much more difficult with a large developer, of course. I hope the client is slowly realizing the kind of performance the MEP (mechanical, electrical, plumbing) designer is delivering here. Still, it’s probably a good business for him. There are a total of 15 housing units; he has a lot of trouble with me, but he makes a high margin with the others.
S
stjoob_at12 Oct 2022 13:09You will most likely have the most efficient system in the entire construction project.
It’s a pity that it is so complicated. A wall heating system isn’t rocket science either. Just the partition wall between the shower and the toilet would provide about 2 times 2 to 2.5 m² (22 to 27 ft²) of heating surface, depending on the wall height... They probably won’t want to deduct an electric towel warmer, radiator, or infrared mirror heater from the heating load either.
The suboptimal design mainly results from the heating load of the bathrooms.
It’s a pity that it is so complicated. A wall heating system isn’t rocket science either. Just the partition wall between the shower and the toilet would provide about 2 times 2 to 2.5 m² (22 to 27 ft²) of heating surface, depending on the wall height... They probably won’t want to deduct an electric towel warmer, radiator, or infrared mirror heater from the heating load either.
The suboptimal design mainly results from the heating load of the bathrooms.
So, here is an update.
The planner has revised the conditions again (primarily the shower as the heating surface, outdoor temperature according to standards, vinyl as the floor covering) and arrived at a bathroom temperature of 23°C (73°F) with a supply temperature of 36°C (97°F). These are all calculated values, but it still feels better than the originally planned 40°C (104°F). What’s really absurd is that the -11.3°C (12°F) outdoor temperature is correct. Regardless of its impact, this means that all calculations over the past 2.5 years were based on incorrect standard values. It’s really a crazy story.
Based on calculations, the planner now suggests pipe spacing of 20 cm (8 inches) on the ground floor and 10-15 cm (4-6 inches) upstairs, which again doesn’t sit right with me. I have a few differences between parquet and vinyl to consider. According to her calculation, for a 15 sq m (161 sq ft) room, she needs either 3 heating circuits with 5 cm (2 inch) pipe spacing (38°C (100°F) supply/parquet) or 2 heating circuits with 10 cm (4 inch) spacing (36°C (97°F) supply/vinyl). I find that quite remarkable if the calculation is correct. On the ground floor, we will go for 15 cm (6 inch) spacing, and upstairs consistently 10 cm (4 inch). This also works well regarding the heating circuit lengths.
As I understand it, I will have to ensure in practice that the bathroom gets warm enough, and if that is the case, I can try lowering the supply temperature further. Is that the right approach?
Of course, I have only seen excerpts again, but I suspect that the heating circuit in the bathroom is the only one with a length significantly longer than the others. I will inquire about that again.
Based on calculations, I am now probably looking at a heating load of roughly 6.3-6.4 kW. That would mean a 7 kW heat pump is rather oversized, but a 5 kW one might not be sufficient, correct? Aside from that, the heat pump has already been ordered, so it will be difficult to change anything now.
Man, I’ll be glad when this whole topic is finally done! 😉
The planner has revised the conditions again (primarily the shower as the heating surface, outdoor temperature according to standards, vinyl as the floor covering) and arrived at a bathroom temperature of 23°C (73°F) with a supply temperature of 36°C (97°F). These are all calculated values, but it still feels better than the originally planned 40°C (104°F). What’s really absurd is that the -11.3°C (12°F) outdoor temperature is correct. Regardless of its impact, this means that all calculations over the past 2.5 years were based on incorrect standard values. It’s really a crazy story.
Based on calculations, the planner now suggests pipe spacing of 20 cm (8 inches) on the ground floor and 10-15 cm (4-6 inches) upstairs, which again doesn’t sit right with me. I have a few differences between parquet and vinyl to consider. According to her calculation, for a 15 sq m (161 sq ft) room, she needs either 3 heating circuits with 5 cm (2 inch) pipe spacing (38°C (100°F) supply/parquet) or 2 heating circuits with 10 cm (4 inch) spacing (36°C (97°F) supply/vinyl). I find that quite remarkable if the calculation is correct. On the ground floor, we will go for 15 cm (6 inch) spacing, and upstairs consistently 10 cm (4 inch). This also works well regarding the heating circuit lengths.
As I understand it, I will have to ensure in practice that the bathroom gets warm enough, and if that is the case, I can try lowering the supply temperature further. Is that the right approach?
Of course, I have only seen excerpts again, but I suspect that the heating circuit in the bathroom is the only one with a length significantly longer than the others. I will inquire about that again.
Based on calculations, I am now probably looking at a heating load of roughly 6.3-6.4 kW. That would mean a 7 kW heat pump is rather oversized, but a 5 kW one might not be sufficient, correct? Aside from that, the heat pump has already been ordered, so it will be difficult to change anything now.
Man, I’ll be glad when this whole topic is finally done! 😉
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