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?
So, I have received some updated information. The supply temperature is now set at 38°C (100°F), as calculations suggest that a lower supply temperature is not feasible. Due to the central exhaust ventilation system without heat recovery, the calculated heating demand is also 45 W/m² (4.2 W/ft²). The bathrooms are now designed for 22°C (72°F) and are still equipped with an electric towel warmer, which is not included in the calculation.
The following information is available to me:
As a layperson, I would say that the heating circuit lengths are quite long, but I am unsure of the actual impact. Additionally, all the long heating circuits are located on the upper floor. Could the slope (pipe gradient) still have a negative effect here, or has this already been taken into account?
The ground floor bathroom seems like it could be designed for 24°C (75°F). Could a supply temperature of 5 cm (2 inches) be chosen directly here?
The following information is available to me:
| Room | Number of Radiators | Supply Temperature (VA) | Radiator Length (cm) |
| Living Room (Ground Floor) | 3 | 15 | 95/117/106 |
| Hallway (Ground Floor) | 1 | 15 | 83 |
| Guest Room (Ground Floor) | 1 | 15 | 80 |
| Guest Bathroom (Ground Floor) | 1 | 10 | 43 |
| Children’s Room 1 (Upper Floor) | 2 | 5 | 132/138 |
| Children’s Room 2 (Upper Floor) | 2 | 5 | 148/156 |
| Bedroom + Dressing Room (Upper Floor) | 3 | 5 | 58/129/128 |
| Bathroom (Upper Floor) | 1 | 5 | 126 |
As a layperson, I would say that the heating circuit lengths are quite long, but I am unsure of the actual impact. Additionally, all the long heating circuits are located on the upper floor. Could the slope (pipe gradient) still have a negative effect here, or has this already been taken into account?
The ground floor bathroom seems like it could be designed for 24°C (75°F). Could a supply temperature of 5 cm (2 inches) be chosen directly here?
R
RotorMotor27 Sep 2022 14:38Somewhat unusual interpretation.
Why are the bedroom/walk-in closet so tight with three circles?
The same applies to the children's room.
Why does the bathroom have only one circle?
Why is the guest bathroom assigned a larger valve actuator than the bathroom?
As far as I know, "slope" does not matter.
Is the upper part of the house, meaning the roof, insulated significantly worse than the rooms below?
Why are the bedroom/walk-in closet so tight with three circles?
The same applies to the children's room.
Why does the bathroom have only one circle?
Why is the guest bathroom assigned a larger valve actuator than the bathroom?
As far as I know, "slope" does not matter.
Is the upper part of the house, meaning the roof, insulated significantly worse than the rooms below?
RotorMotor schrieb:
Why are the bedroom/walk-in closet zones so small with three circuits? Apparently, this is to reach about 20°C (68°F) room temperature. However, these areas will most likely not be heated regularly.
RotorMotor schrieb:
The same applies to the children's rooms. This also seems necessary to reach 20°C (68°F). There is even a slight undersizing (1W/20W). If three heating circuits were installed in these rooms, wouldn’t the heating output improve?
RotorMotor schrieb:
Why does the bathroom have only one heating circuit? No idea, perhaps to save heating circuits?
RotorMotor schrieb:
Why does the guest bathroom have a larger heating surface area than the main bathroom? Probably also to reach just 22°C (72°F).
RotorMotor schrieb:
Is the attic or roof significantly less insulated than the rooms below? This is a developer project, so I don’t have access to all the documentation, but it seems to be the case. It doesn’t appear to be related to the exterior walls. Children’s room 1 has only one small exterior wall, with the rest being shared walls with the adjacent terraced house and children’s room 2. Children’s room 2 has two long exterior walls. The different heating demand between the ground floor and upper floor is quite noticeable.
R
RotorMotor27 Sep 2022 14:59Pacmansh schrieb:
It’s probably necessary to reach the 20°C (68°F). There is even a minimal underperformance (1W/20W). If three heating circuits are installed here each Please add the desired temperatures as well as the over- and underperformance figures if you have them.
None of this really seems to make much sense to me.
I can no longer edit the table above. Originally, 24°C (75°F) was planned for the bathrooms and 20°C (68°F) for the other rooms. This was changed to 22°C (72°F) for the bathrooms and 20°C (68°F) for the other rooms to achieve a lower ventilation heat loss on the ground floor.
I am not familiar with overlaps. At the moment, I only have the information: Children’s room 1, 1 watt underperformance; Children’s room 2, 20 watts underperformance.
I am not familiar with overlaps. At the moment, I only have the information: Children’s room 1, 1 watt underperformance; Children’s room 2, 20 watts underperformance.
I'll leave the bedroom aside for now. Is the statement regarding the two children's rooms correct?
Dividing the system into three heating circuits would reduce the temperature differential and increase the heat input into the rooms. The same would also apply to the bathroom.
The guest bathroom could easily be set to 23°C (73°F) and the flow rate could be lowered back to 5cm (2 inches). It was already at that level with a 40°C (104°F) supply temperature and a 24°C (75°F) target temperature.
Dividing the system into three heating circuits would reduce the temperature differential and increase the heat input into the rooms. The same would also apply to the bathroom.
The guest bathroom could easily be set to 23°C (73°F) and the flow rate could be lowered back to 5cm (2 inches). It was already at that level with a 40°C (104°F) supply temperature and a 24°C (75°F) target temperature.
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