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:
What type of heat pump is being installed? I only have incomplete information on that as well. So far, I know that a Vaillant Arotherm Split VWL 75/5 AS with uniTower VWL 78/5 IS has been ordered. We’ll see what will be available and when. Judging by the current progress, I think the developer will probably be finished by February/March. However, I don’t expect the heat pump to be there by then. It was apparently only ordered 2-3 weeks ago.
Joedreck schrieb:
I find the whole approach of the planners disrespectful and unprofessional. But oh well, you’re stuck with it. That’s true. They probably thought it was easy money. The project has a total of 15 residential units, quickly processed through the software and done. But many things in the planning were really poor. A lot could be resolved, a few issues had to be accepted, but so far the contractors on site seem to be doing a good job. I haven’t reached the sanitary installers yet, maybe they also hired good people there.
I have reviewed the standards again and am now quite sure that the lower outdoor temperature should have been used. That would naturally be a strong argument to bring up with the MEP engineer. I also have to explain to the developer why I am causing so much trouble and questioning nearly every decision of the MEP engineer. This of course leads to extra effort, which they would like to pass on to me. If I then say that the planning was based on outdated standards, I should have a strong case that the additional planning should not be at my expense.
R
RotorMotor7 Oct 2022 11:18If the planner designs the hydraulics for -16, that is clearly better for you than -11.
So it could be that you are actually causing a deterioration for yourself.
I also don’t see much advantage in continuing to discuss the TGA. Either you do it yourself, have it done externally, or accept the average solution. 😉
So it could be that you are actually causing a deterioration for yourself.
I also don’t see much advantage in continuing to discuss the TGA. Either you do it yourself, have it done externally, or accept the average solution. 😉
The discussions will mostly be over by Monday as well. That’s when the planning is supposed to be discussed. Doing it yourself or outsourcing is unfortunately no longer an option. I have already come to terms with an average solution.
Is that really the case? I would have thought that the planned supply temperature could then be chosen a bit lower, and also that the rooms might be better balanced in relation to each other. I could also imagine that the long heating circuits might be somewhat reduced.
Do you mean it would be worse to calculate with –11°C (12°F) because, for example, the required pipe spacing might have to be increased?
RotorMotor schrieb:
If the planner designs the hydraulics for –16, that is definitely better for you than –11.
Is that really the case? I would have thought that the planned supply temperature could then be chosen a bit lower, and also that the rooms might be better balanced in relation to each other. I could also imagine that the long heating circuits might be somewhat reduced.
Do you mean it would be worse to calculate with –11°C (12°F) because, for example, the required pipe spacing might have to be increased?
-11°C (12°F) or -16°C (3°F) shouldn’t really make a big difference in the installation spacing. So, at this point, you have no other choice but to go through with it.
Only the heat pump definitely shouldn’t be larger than 7kW, according to your heating load at -16°C (3°F). There would have been room to optimize by choosing a 5kW heat pump.
Only the heat pump definitely shouldn’t be larger than 7kW, according to your heating load at -16°C (3°F). There would have been room to optimize by choosing a 5kW heat pump.
The 7 kW (9.4 hp) heat pump is currently planned. I don’t expect the team will be able to optimize it down to 5 kW (6.7 hp). In the end, the planner has to take responsibility that the required temperatures will be reached, and I’m sure they won’t want to accept that responsibility. I also think the house itself won’t support that.
The meeting went basically well, although somewhat strangely. I had prepared several topics, and with every question, the planner hesitated, didn’t really know how to answer, had to look up values that she could only explain after much discussion, etc. It basically came down to repeatedly hearing, “This is what the software calculated; I don’t know where that comes from.” If I were in their place, I would have been embarrassed, and now I can understand why they were reluctant to release the plans. This doesn’t help me too much yet, but at least it gives me a good feeling, and since I was able to point out several errors, I also have strong arguments that the builder cannot charge me for the extra planning effort. Regarding the question of which standard outdoor temperature must be used, no answer was found either. I referred to the standard, and the planner said, “We only enter a postal code in the software; we can’t change the value.” We will have to wait and see how that develops.
The most important point was that I noticed the shower in the main bathroom was not counted as a heating surface. So, we have a bathroom of 9.5 m² (102 ft²), but only 6.1 m² (66 ft²) was considered as heating surface (subtracting the shower and bathtub). The shower will now also be counted as heating surface, which gives us about 1.6 m² (17 ft²) or 25% more heating area. In the other rooms, they had calculated with parquet flooring instead of vinyl, which is now going to be corrected.
Other points were that they only calculated bathroom temperatures of 22°C or 24°C (71.6°F or 75.2°F) — “23°C (73.4°F) is an odd number” — and that the pipe spacing could only be adjusted in 5 cm (2 inches) increments (“it’s not possible otherwise in the panel system”). Since I don’t find the number 23, despite it being a prime number, to be a problem at all, and since we are not using a panel system but a staple fixing system, there’s additional potential for optimization here.
Long story short: a new plan will be made again, for which I now have a bit more hope that, within an average planning framework, it will be closer to a 3+ rather than a 4-. We’ll see.
The meeting went basically well, although somewhat strangely. I had prepared several topics, and with every question, the planner hesitated, didn’t really know how to answer, had to look up values that she could only explain after much discussion, etc. It basically came down to repeatedly hearing, “This is what the software calculated; I don’t know where that comes from.” If I were in their place, I would have been embarrassed, and now I can understand why they were reluctant to release the plans. This doesn’t help me too much yet, but at least it gives me a good feeling, and since I was able to point out several errors, I also have strong arguments that the builder cannot charge me for the extra planning effort. Regarding the question of which standard outdoor temperature must be used, no answer was found either. I referred to the standard, and the planner said, “We only enter a postal code in the software; we can’t change the value.” We will have to wait and see how that develops.
The most important point was that I noticed the shower in the main bathroom was not counted as a heating surface. So, we have a bathroom of 9.5 m² (102 ft²), but only 6.1 m² (66 ft²) was considered as heating surface (subtracting the shower and bathtub). The shower will now also be counted as heating surface, which gives us about 1.6 m² (17 ft²) or 25% more heating area. In the other rooms, they had calculated with parquet flooring instead of vinyl, which is now going to be corrected.
Other points were that they only calculated bathroom temperatures of 22°C or 24°C (71.6°F or 75.2°F) — “23°C (73.4°F) is an odd number” — and that the pipe spacing could only be adjusted in 5 cm (2 inches) increments (“it’s not possible otherwise in the panel system”). Since I don’t find the number 23, despite it being a prime number, to be a problem at all, and since we are not using a panel system but a staple fixing system, there’s additional potential for optimization here.
Long story short: a new plan will be made again, for which I now have a bit more hope that, within an average planning framework, it will be closer to a 3+ rather than a 4-. We’ll see.
Realistically, you won’t be able to plan it “optimally.” You lack the right partner and the necessary influence for that. It’s not a single contract award after all.
But considering the circumstances, you’re already miles ahead of many others in your situation. You can optimize, and the remaining 10% won’t make much difference in the end.
I haven’t reread the entire thread.
One thing that just came to mind and might still be influenced is... where are the thermostatic radiator valves (TRVs) located? Ideally, you would place them sensibly in bathrooms because they emit heat. In the bathroom, this helps since it’s already a tight space. In the hallway, storage room, or utility room, it’s basically pointless, and no additional heat is needed or desired.
If they are in the hallway, make sure the supply pipes are insulated. Otherwise, you might get the effect that even when you turn off the heat in the hallway, it remains warm due to heat being transferred through the pipes, whereas the bathroom needs that warmth more.
But considering the circumstances, you’re already miles ahead of many others in your situation. You can optimize, and the remaining 10% won’t make much difference in the end.
I haven’t reread the entire thread.
One thing that just came to mind and might still be influenced is... where are the thermostatic radiator valves (TRVs) located? Ideally, you would place them sensibly in bathrooms because they emit heat. In the bathroom, this helps since it’s already a tight space. In the hallway, storage room, or utility room, it’s basically pointless, and no additional heat is needed or desired.
If they are in the hallway, make sure the supply pipes are insulated. Otherwise, you might get the effect that even when you turn off the heat in the hallway, it remains warm due to heat being transferred through the pipes, whereas the bathroom needs that warmth more.
Similar topics