ᐅ Challenges for MEP planners: underfloor heating flow temperature and wastewater ventilation

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?

Pacmansh schrieb:

Point 1) Supply temperature for underfloor heating, new build, 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. That seems absurdly high to me. Additionally, I was told that the surface temperature is designed to a maximum of 27°C (81°F) due to the floor coverings. That doesn’t seem to add up for me. When I asked about lowering the supply temperature, the response was, "A general reduction is not possible with the underfloor heating without reducing the pipe spacing to an impermissible level."

Do you have any ideas on how I can respond to this more professionally? Are there any documents or sources I can refer to, or information I should request?

What does the room-by-room heat load calculation and current heating system design look like? 40°C (104°F) is not up to date.
The pipe spacing is usually planned appropriately. 5cm (2 inches) is the minimum. In that respect, the developer’s statement is complete nonsense.
You can only argue effectively once you have the detailed planning documents.

The frustrating part is that this statement does not even come from the builder, but from the HVAC engineer they hired.

At the moment, I do not have any information regarding the heating load calculation or the heating system design. I will need to request that again. I only have the contractual documents stating, "The heating system will be designed for the coldest day according to the standard and for the following indoor temperatures of the rooms" (bathroom 24°C (75°F), other rooms 20°C (68°F)).

I will try to obtain further information.

Pacmansh schrieb:

Hello,
we are at the beginning of the construction phase for our developer project and I am having some disagreements with the HVAC planner. To be better prepared for the discussion, I would really appreciate your assessment.

Point 1) Flow temperature for underfloor heating, new build, KfW55 standard, air-to-water heat pump
The flow temperature for the underfloor heating (end-terrace house on both floors) was given to me as 40°C (104°F) after inquiry. That seems absurdly high to me. I also confirmed that the surface temperature is designed to be a maximum of 27°C (81°F) due to the floor coverings. Somehow, this doesn’t seem to add up. When I asked about lowering the flow temperature, the reply was: “A general reduction is not possible with underfloor heating without reducing the pipe spacing to an unacceptable level.”

Do you have any ideas on how I can respond to this in a reasonably professional way? Are there any documents or sources I could refer to, or any information I should request?

I can only comment on point 1 from my own experience. First, you should check how the underfloor heating is planned. Because even the latest equipment won’t help if the installation is poor. Important factors to consider are pipe spacing—max. 10 cm (4 inches) —and a maximum pipe length of 80 m (262 feet). There should also be a sufficient number of heating circuits. We have 27 heating circuits. Our pipe spacing is between 6.5 cm (2.6 inches) and 13 cm (5 inches). We expect a flow temperature (brine-water heat pump) of approximately 28–30°C (82–86°F). Here is our installation layout.

It probably won’t help much anyway; the developer’s influence on the execution will be limited. At most, he can now try to communicate his willingness to upgrade to his developer and have the MEP (Mechanical, Electrical, and Plumbing) planner set requirements based on that. But these must come from the developer.

Thank you for the plan and the additional information.

It is true that I don’t have much direct influence in this matter myself. However, since the developer and the MEP planner are two separate companies, it hasn’t seemed so far that reasonable changes were rejected.

And if I can explain to the developer that the MEP planner is making (or saying) nonsense, then I do have some hope. The statement "We have to run a flow temperature of 40°C (104°F) because otherwise we fall below the allowed pipe spacing" sounds like complete nonsense, doesn’t it?