MVHR: Don't get seduced by SFP alone - Greenwood


29 October 2013

MVHR: Don't get seduced by SFP alone

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Energy performance in SAP is just one of the key considerations for MVHR specification - don't let it rule your head when choosing a unit - you also need to consider noise, airflow performance and ease of installation to determine total cost effectivenss!


 Achieving Guaranteed Installed Performance when it comes to MVHR is more crucial than ever now a 2 year BRE study is complete and found issues with 10/10 of the installed units.
It goes without saying that on-site practise and delivery is well and truly under the microscope now we are 3 years to the introduction of Guaranteed Installed Performance criteria through Building Regulations ADF:2010 and the Domestic Ventilation Compliance Guide. 

For the first time, installers are now a core part of the compliance and sign off process and this recent study has suggested far more focus is required when it comes to MVHR.

The thing about MVHR is that it is a SYSTEM – a whole house system that in actual fact now provides 100% of the required ventilation to a new dwelling since the infiltration aspects of the calculation have been removed.  We are building more airtight and efficient homes, and 2010 Building Regulations drive this forward with increased ventilation rates.

So – what do we need to do to ensure we get MVHR right - here are 3 simple considerations...

1. Don't be sedcued by SFP performance alone 

Specific Fan Power (SFP) gives you a good indication of energy performance and therefore reward in SAP for Part L, but don’t get carried away.  Time after time, we have looked at designs and visited installations where Noise from the MVHR system has become an issue. 

The root cause is always that the MVHR Unit has not been specified correctly.

Yes it has low energy performance and has enabled a good reward in SAP, but it doesn’t have the airflow capacity to deliver the performance effectively – e.g. it has to be run at 80% capacity and that means noise!!  SFP is just one part the equation.  Look at dwelling size and layout and the airflow graphs provided for the product.  Match the unit to the property, not find the most energy efficient unit and go with it.

2. Consider the DUCTING!

 Remember we are in SYSTEM land here. MVHR = Unit + Ducting, so why spend considerable time specifying the unit and then choosing ducting which can’t support the overall objective of Guaranteed Installed Performance.

Ducting comes in many shapes, types and sizes and it is its composition AND the quality of the installation that completes the SYSTEM which then delivers the performance.

  • Choose a ducting system which aligns with Guaranteed Installed Performance.
  • Choose a ducting system that is quick and easy to install and work with the structure of the building, rather than against it – what if you could run a continuous length of ducting through and around the joists, rather than have to join a load together?
  • Choose a ducting system that is robust enough to handle all stages of the building process – that can’t be crushed and has good airtight sealed connection points
  • Choose a ducting system that can be cleaned for the long term provision of indoor air quality and performance.
  • Choose a ducting system that reduces noise transfer between rooms and within the entire MVHR system itself.
  • Choose a ducting system that has 75% less connection points so that air leakage is eliminated.
  • Choose a ducting system that means you can leave the duct tape or sealant in the van!!

Focusing on a ducting system with all of these benefits and design aspects are critical in achieving the best performance for the MVHR system in the home.

3. Make sure installers understand MVHR and can install and commission the system effectively

Idealism meets Realism on-site and we have to be tuned into both in order that there is a seamless approach to Guaranteed Installed Performance.

Installing a system incorrectly will only result in one thing – non-compliance to Building Regulations.  It will also result in, if not immediately, issues with the homeowners concerning noise, draughts, over-heating and even incidents where condensate collects in the wrong side of the unit and damages not only the product, but all of the ceiling/floor above and below it.

The BPEC Accredited Domestic Ventilation Installation Training course is available now to provide installers with the key considerations and understanding for MVHR installation from design through installation and then commissioning.  BPEC accredited installers offer even further reward in SAP too.  Installers are now being targeted for the first time through Regulations so this training is crucial to ensuring GIP is achieved on site.  MVHR is a SYSTEM installation and much more involved than a traditional extract fan.

BPEC2U training is available now – at your premises for your installers or for you, saving overnight accommodation and travelling expenses and delivered in one single day.  Book or call now for more information 01903 777135

So I suppose what we are trying to say is...

From the very outset the installation of a MVHR system may look just like another ventilation job, there is in fact a mix of operational, professional and external influencers to ensuring the installation not only meets Building Regulation requirements, but is also fully fit for purpose in the long-term. By understanding the different parameters and looking at the whole system as oppose to the parts, installers will go a long way to securing their own reputation and assuring the use of MVHR units for the future. Don’t get seduced by a really low energy figure alone, don’t just think about cost – don’t just think about fitting the unit in the loft - think about the entire system!

 A 1.4 Petrol and a 2.0 TDI Volkswagen Golf look the same from the outside, but drive them in a race and one will win hands down – use the same philossophy and make sure the product is fit for purpose  - Above everything else Guaranteed Installed Performance should be at the top of the agenda.


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