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?
R
RotorMotor14 Oct 2022 10:39@bortel and @SaniererNRW123 the effort might not be proportional to the savings in this case.
As mentioned, the bathroom is already at its limit. So it either needs wall heating or an electric supplementary heater, which again leads to disproportionate effort.
Here too, the Pareto principle should be applied.
As mentioned, the bathroom is already at its limit. So it either needs wall heating or an electric supplementary heater, which again leads to disproportionate effort.
Here too, the Pareto principle should be applied.
I don’t understand how you can already estimate the effort/benefit? Do you know the figures for additional costs and future energy prices?
Especially now, when utility costs keep increasing, I also don’t quite get why a few extra meters of pipe and possibly a floor heating system should be so expensive... Chipping off plaster, laying the floor heating, replastering, done... sometimes you just have to be pragmatic.
Alternatively, install an electric cable ladder.
I can only advise everyone to pay explicit attention to this. Once the screed is installed, it’s too late.
Especially now, when utility costs keep increasing, I also don’t quite get why a few extra meters of pipe and possibly a floor heating system should be so expensive... Chipping off plaster, laying the floor heating, replastering, done... sometimes you just have to be pragmatic.
Alternatively, install an electric cable ladder.
I can only advise everyone to pay explicit attention to this. Once the screed is installed, it’s too late.
S
SaniererNRW12314 Oct 2022 10:57RotorMotor schrieb:
As I said, the bathroom is already at its limit.I’m not sure how you currently use your new builds. But from my experience, all the doors in the house tend to be open. In that case, the temperature in every room is usually around 22°C (72°F). Therefore, I don’t see any real issues with the bathroom.So, in the bathroom the door is usually closed, and the bedroom as well. Otherwise, you’re right, it will all balance out over time.
According to calculations, the heating with vinyl flooring and a 36° Celsius (97°F) flow temperature should be installed at 20cm (8 inches) spacing on the ground floor and 10 to 15cm (4 to 6 inches) on the upper floor, with the main bathroom at 5cm (2 inches) and the guest bathroom at 10cm (4 inches).
We are now installing with 15cm (6 inches) spacing on the ground floor (so slightly closer) and 10cm (4 inches) on the upper floor (also a bit closer). All bathrooms at 5cm (2 inches) since there is nothing to adjust without wall heating. Electric bathroom heaters will add some extra warmth but are not included in the calculations.
So, based on intuition, I would say the actual flow temperature in real conditions might be a bit lower, while the temperature in the living room will probably be more around 21 to 22° Celsius (70 to 72°F) rather than the design temperature of 20° Celsius (68°F). I think the spacing is more or less appropriate for the bathrooms; with 5cm (2 inches) in the living/dining area, we wouldn’t gain anything anyway.
Right, the effort plus the planner’s fees, which are probably around 200€ per hour and might take about 5 hours for this additional planning. The general contractor also charges higher hourly rates because this deviates from the original scope, plus a 25% margin from the developer and 19% VAT... it adds up quickly.
According to calculations, the heating with vinyl flooring and a 36° Celsius (97°F) flow temperature should be installed at 20cm (8 inches) spacing on the ground floor and 10 to 15cm (4 to 6 inches) on the upper floor, with the main bathroom at 5cm (2 inches) and the guest bathroom at 10cm (4 inches).
We are now installing with 15cm (6 inches) spacing on the ground floor (so slightly closer) and 10cm (4 inches) on the upper floor (also a bit closer). All bathrooms at 5cm (2 inches) since there is nothing to adjust without wall heating. Electric bathroom heaters will add some extra warmth but are not included in the calculations.
So, based on intuition, I would say the actual flow temperature in real conditions might be a bit lower, while the temperature in the living room will probably be more around 21 to 22° Celsius (70 to 72°F) rather than the design temperature of 20° Celsius (68°F). I think the spacing is more or less appropriate for the bathrooms; with 5cm (2 inches) in the living/dining area, we wouldn’t gain anything anyway.
bortel schrieb:
I don’t quite understand why a few more meters of pipe and possibly a wall heating should be so expensive... breaking open the plaster, installing the wall heating, replastering, done... sometimes you have to be pragmatic.
Right, the effort plus the planner’s fees, which are probably around 200€ per hour and might take about 5 hours for this additional planning. The general contractor also charges higher hourly rates because this deviates from the original scope, plus a 25% margin from the developer and 19% VAT... it adds up quickly.
S
SaniererNRW12314 Oct 2022 11:30Pacmansh schrieb:
Correct, the effort plus the effort for the planner, who surely charges around €200 per hourThe planning, including the installation plan, costs about €150 at an external engineering office. However, this is not per hour but a flat rate. So, the effort during house construction is negligible.Similar topics