Frequently asked questions
Q. Why do I need MVHR?
A. MVHR continually removes moist, stale air from your home and brings in fresh air, at room temperature.
This provides a superior environment for your health and also saves on heating bills, because now you do not need to let in cold air to keep the home environment healthy.
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Q. What is included in installation?
A. Everything except:
1. Coring large holes for intake and exhaust grilles (best to hire in a specialist core driller)
2. Connecting unit condensate drain to internal plumbing (simple job for a plumber)
3. Wiring unit for power and remote control (simple job for an electrician)
4. Installing roof terminals (simple job for a roofer)
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Q. Is MVHR a heating system?
A. Not as such, no. Standard MVHR does not heat a home.
Adding extra heat to the air can be designed in, however this is only suitable for homes with very high levels of insulation and a low airtightness score (below 1 ACH @ 50Pa).
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Q. How loud is it?
A. If your system is designed and supplied from a reputable company, and I install it, the system will be effectively inaudible in all rooms except the room in which the MVHR unit is located. The kitchen grille will typically be under 25dB(A) and living spaces typically under 20dB(A), well under building regs limits. New owners are often delighted to find they cannot hear anything from the air valves.
It is good practice to install an MVHR unit in a utility or plant room, where a low hum will not bother anyone. Also, enclosing the unit in a cupboard will reduce its breakout noise significantly.
That said, bedroom cupboards are not recommended!
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Q. Does MVHR cure damp and mold?
A. If the root cause of mold and damp is water leaking into the home via the building fabric - from damaged roofs, guttering, pointing etc, then clearly MVHR cannot solve that problem. However, the majority of mold and damp occurs not from leaks, but due to an environment in which there is insufficient ventilation, because humid air is not escaping and can even condense on cold walls, ceilings, windows etc.
In this case, MVHR will often eradicate the issue because it is continually changing the air in the house (usually 0.3 - 0.4 air changes per hour (ACH). Furthermore, while up to 90% of the heat will be recovered, not all of of the moisture will be - some of it is drained away. Therefore MVHR has a slightly dehumidifying effect on the air in the home.
Personal anecdote - following the installation of MVHR in my house, the average relative humidity dropped from 70 - 80% to 50 - 60% (40 - 60% is considered ideal) and visual proof of this is I no longer wake up to condensation on my (double glazed) windows. And remember, less humid air is easier to heat!
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Q. Can my MVHR unit go in the loft?
A. If it is a warm loft, certainly. What is a warm loft, you ask? A warm loft is where the insulation is within or around the roof structure, making the loft beneath it 'warm'.
A cold loft is therefore one in which the loft insulation is under/at the loft floor level. If your unit and ducting is above this insulation, clearly you are going to lose a significant amount of the heat you just have recovered - which will render the system pointless. However, it can be done provided the unit is within an insulated cupboard and the ducting is laid under loft insulation. This must be done thoroughly: if the insulation laid over ducts is patchy in only a couple of places, then this will result in significant heat loss.
In general, it is better to make provision for the unit and ducting within the thermal envelope, if possible.
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Q. Where does the ducting go?
A. A good designer will look to run ducts within floor joists, stud walls and any useful voids you may have. It will be their aim to not need any boxing in, bulkheads, lowered ceilings etc to hide ducts, though sometimes these things are unavoidable.
For those who like the industrial look, spiral galvanised steel ducting can look quite stylish when left exposed.
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Q. Are you insured?
A. Yes: Public Liability £1m; Professional Indemnity £1m.
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Q. Why should you install my system?
A. Despite MVHR not being difficult to install, I have seen far too many badly installed systems, resulting in poor aesthetics and poor performance. Leaving aside poor fitting skills, this is likely due to rushing the install and not understanding how the system works. My background as a designer sets me apart in this regard.
