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Humidity control of single-family air handling units

Buildings have become more air tight and rotary heat exchangers are the most common resulting in risk of moisture damage. Studies have shown that units can be controlled, minimizing these risks. The project aims at developing a method of testing how air handling unit control systems can handle internal moisture generation.

Aim and goal

The overall goal of the project is a methodology for real-time dynamic testing of the control system of bi-directional ventilation units in single-family houses regarding heat recovery, pressure balance and moisture control. In the long term, the goal is that these units shall be used in the well-insulated and air-tight houses of the future without the risk of unwanted side effects in the form of moisture damage on the building envelope.

 

The sub-goals of the project are the following:

  • Create different realistic moisture load profiles (low-medium-high)
  • Create mathematical models of some typical single-family houses
  • Create physical connection between air handling unit and test facility
  • Create input and output interface between the units and house models
  • Test out the methodology on units with different heat exchanger types
    and different control systems
  • Describe the test methodology in a report

 

Challenge

Future tightening of energy requirements in the Swedish building regulations is expected to lead to increased use of bi-directional ventilation units with heat recovery in Swedish single-family houses. In a presentation at a seminar in 2017, experiences from several newer single-family houses with bi-directional ventilation units were reported and where moisture damage was suspected to be due to the ventilation system. The presentation also presented driving forces for moisture convection and how these are affected by the ventilation system. The conclusion was that in a future large-scale use of bi-directional ventilation units in single-family houses must ensure a correct pressure balance and that eventual moisture return can be limited. Otherwise, there is a risk that in a few years we will get new newspaper headlines about moisture damage in newly built houses (similar to what happened with the single-stage sealed facades).

Boverkets föreslagna skärpningar av energikraven i BBR fr.o.m. 2020 förväntas leda till en ökad användning av FTX i svenska småhus.
 

Solution

Ett flertal studier har dock visat att det teoretiskt är möjligt att styra luftflöden, och i förekommande fall rotorvarvtal, på ett sådant sätt att risk för konvektionsfuktskador minimeras. Om man kan kontrollera tryckskillnaden över klimatskärmen så att övertryck mot ute undviks behöver inte ett något förhöjt fukttillskott innebära någon risk för fuktkonvektionsskador. I vissa fall kan det t.o.m. vara en fördel om man med en roterande värmeväxlare och närvarostyrd ventilation under kontrollerade former kan åstadkomma ett något förhöjt fukttillskott. Både människors slemhinnor och inredningsmaterial såsom exempelvis stora parkettgolv skulle må bra av om antalet timmar under 30 % relativ fuktighet.

 

Effect

Genom att säkerställa att styr- och reglerfunktion hos FTX-aggregat i småhus fungerar på ett optimalt sätt med avseende värmeåtervinning, tryckbalans och eventuell fuktåtervinning kan en storskalig introduktion av FTX-ventilation i nybyggda, välisolerade och lufttäta småhus ske utan risk för ”bakslag” i form av fuktskador på klimatskärmen vid användning av FTX-ventilation.

 


Summary

Project name

Humidity control of air handling units

Status

Active

RISE role in project

Projektledning och genomförande

Project start

Duration

2020-10-31

Partner

www.flexit.se, www.ostberg.com, www.rec-indovent.se, www.swegon.se, www.systemair.com, Ventener AB

Funders

www.energimyndigheten.se, www.flexit.no, www.ostberg.com, www.rec-indovent.se, www.swegon.se, www.systemair.com

The UN sustainable development goals

3. Good health and well-being
7. Affordable and clean energy
9. Industry, innovation and infrastructure
11. Sustainable cities and communities
13. Climate action

Coordinators

Project members

Svein Ruud

Contact person

Svein Ruud

Teknisk lic

+46 10 516 55 14
svein.ruud@ri.se

Read more about Svein