HRV and fire

I don't believe the risks are understood - or if they are - that they being addressed by the HRV industry

http://www.boards.ie/vbulletin/showthread.php?t=2055385732&highlight=fire

Be aware of some unfortunate Canadian experience with the units CAUSING fires

http://www.bamn.org/prHRVrecall.cfm

http://www.nachi.org/forum/f48/venma...concern-11412/

http://www.bluemountainscourierheral.../article/61577

Perhaps Paul in Montreal can put a perspective on the reports ?

My experience of talking to "the HRV industry" in Ireland is that the "double glazing /2nd hand car merchant" has found a new opportunity . Ask them any hard questions at trade fairs and see them spoof and flap .

I my view that industry , in Ireland anyhow - and I suspect in the UK too - does not know or care about the issues I have posted in this thread .

"Build tight and ventilate right" - a snappy Blairite sound bite - that's all . My view .

Proceed with caution .

That first report seems to me to be pointing out areas where there may be a risk, not where products are systematically causing problems. The risks include 'the HVAC may be dirty when installed' (is that really something that can't be fixed?) and 'poor control of temperature...due to absense of cooling' (should you be suprised if a ventilation system cannot act like an air conditioner?). Hmmm...

The vague reference to health problems is so inconclusive that I cannot take it seriously. My sister's house has a fusty old hot air heating system from the 70's and I can fully understand how that might affect the occupant's health, as might communual systems in the apartment blocks common in Europe. A modern domestic system would appear to have no obvious vector for health problems and other than the issue of humidity, shows little difference from just opening the windows. In fact, the possibility of dust and allergen free ventilation should offer better air quality?

The only real lesson to take from that report is that if you install a ventilation system, or buy a house with one installed, you should commit to regular maintenance cycles. In that sense, it's no different from the maintenance you should carry out on your hot water system (you do get your boiler serviced on an annual basis don't you?).

As for the fire risks.. I'm really not sure about those. In a domestic setting, proper use of smoke alarms and the relatively limited scope of a ventilation system seem to mitigate the actual risk. In apartment blocks and large institutional settings I would imagine the risks to be much more severe.

In general, ventilation systems blow fresh air from the outside into the living areas, which would suggest that transmission of smoke through a building would be reduced in the first case? sinnerboys link seem to be a bit broken so I'm not sure how much of a risk HVAC systems play in small domestic installs as distinct from larger and communual systems.

The link about fire risk is broken - so to summarise

Any upper floor in any house must be min 30 mins fire resistant . So the typical timber floor requires a fully intact floor deck ( t+g / osb / ply etc ) and fully intact ceiling below . Where plasterboard is cut away for vent grilles - the fire resistance is lost .( This dawns on some - not all - in the case of recessed lighting too )

A fire

http://www.youtube.com/watch?v=TKPfkrGDv7U&feature=related

http://www.youtube.com/watch?gl=GB&hl=en-GB&v=jQV_MJwYQ3k&feature=related

will very quickly melt the outlet and attack the floor cavity

Unless you fit one of these at each outlet

http://www.scottaire.co.uk/circularvalves2.html

The fan unit should also be linked to the fire alarm / smoke detector installation to power down .

( but don't bother asking anyone in the industry about this .... they'll think your mad )

Posted By: tomsuswebAnyone want to defend HRV a bit? I was starting to be converted. Are Sinnerboy's fears sensible? Or if it's installed and maintained correctly will you end up with much better air quality?

Tom - I am not attacking HRV ( MVHR ) .

I am saying there are risks . If you are a self builder and informed - that's fine . If you are a disinterested tenant however ... Well we live in a "set and forget" culture . Filters won't be replaced . Filters ARE NOT being replaced People will get sick .

I can "see" before too long Paxo on BBC2 getting stuck into some industry spokesman / environment minister ....

I'm planning to use MVHR as an element of a low energy renovation of
my house.

To gather information I have looked at the websites of manufacturers
of what I perceive as high quality systems (eg. Drexel und Weiss,
Paul, Zehnder Comfosystems). In their native territories they appear
to operate as one-stop-shops for whole MVHR systems with a design
service, their own range of air distribution products, air inlets and
outlets, and other accessories. For example, Zehnder Comfosystems
have their own ComfoTube duct system with a smooth, hygenic lining
(Clinside). One of their brochures shows a miniature chimney sweep's
brush to clean it.

My impression of the UK market is that suppliers use a MVHR unit,
possibly badge engineered to their own branding, with a ducting system
from another manufacturer. I'm not sure if this is because of UK
specific regulations or for other reasons.

While it is relatively easy to find sales literature on a wide variety
of MVHR systems I have yet to find a good review of MVHRs and the
features that are appropriate for the UK climate. Something that
would answer questions such as these:

* What is required for fire safety; frost protection; humidity
control (enthalpy heat exchanger); cleaning and routine
maintenance?

* Does the MVHR control system need to be aware of wet room use?

* Does the MVHR control system need to interact with the cooker
hood?

* Will a ground loop (brine or air) provide a useful amount of
cooling in a UK heatwave?

I would rather be in the position where I could specify the MVHR
system requirements rather than being sold a system that suits a sales
person's requirements!

There is some useful information in this forum and the AECB Forum
(http://www.aecb.net/forum) has more technical information.

Anyone know of a good, up-to-date MVHR review?

Posted By: john_connett'm confused by these comments as both fusible links and intumescent collars depend on heat to activate them. Granted, the fusible links may be quicker in operation. Isn't the major risk in fires from smoke and other combustion products that may be spread through ducting for some time before heat activated devices operate?

Over here, where HRV and ducted air heating systems are common, no-one uses fusible links or intumescent collars in residential applications. If you want to be extra careful, link your smoke detector to the power supply of the HRV so it is shut off if smoke is detected.

Paul in Montreal.

Posted By: Paul in MontrealOver here, where HRV and ducted air heating systems are common, no-one uses fusible links or intumescent collars in residential applications. If you want to be extra careful, link your smoke detector to the power supply of the HRV so it is shut off if smoke is detected.

Paul in Montreal.

Posted By: sinnerboyHRV and fire

I don't believe the risks are understood - or if they are - that they being addressed by the HRV industry

The majority of houses in North America (particularly the US) have forced air heating systems. These carry 10x the volume of air that an HRV system does. If there were serious fire issues with this type of heating system, then we'd be hearing about it in the news all the time. Not that there are no risks, but the mitigation of the risk is a set of good smoke detectors. That's the compromise that's used.

I couldn't find any references to the dangers of forced air heating/cooling systems with respect to fire in residential construction.

With a good smoke and/or CO detector coupled to the HRV's fan control, I really don't think the risk is any worse than an open window (which also increases the rate of spread of fire and smoke).

Paul in Montreal.

I've seen many videos of house fires. The one common element is polyurethane foam in furniture as the biggest risk. Oh, and chip pans. I've seen the recall notices about the HRVs you mention above - but I haven't seen any reports of actual fires over here caused by them, let alone enhanced by the system. As I said, most people have forced air heating/cooling and the duct sizes and air volumes transported are much larger. Best way to reduce house fires is to ban smoking indoors and the cooking of chips. Washing machines are also a surprisingly large source of housefires (water + electrics is not a good combination) as are dishwashers, particularly those which have heating elements from drying which can set plastic items on fire etc. You're correct that air ducts are a risk, but this has to be set in proportion to everything else. Without a smoke detector, you're toast, as it were, no matter if you have an HRV or not. I suspect it's fear of the unusual as such systems are rare in the UK - just like many people here are terrified of gas stoves because they associate gas with explosions. And, of course, houses do explode due to gas leaks - probably more than burn down due to HRV enhanced fires.

Paul in Montreal.

p.s. I have both gas stoves and forced air heating / cooling (in one house) as well as all three in the other

Posted By: john_connett
* What is required for ; cleaning and routine maintenance?

Canadian advice here

from the Canada Mortgage and Housing Corporation recently, on what you need to do to keep your MVHR (which they refer to as HRV) systems tickety-boo.

MAINTAINING YOUR HEAT RECOVERY VENTILATOR (HRV)

Your heat recovery ventilator (HRV) can help make your house a clean, healthy living environment, while keeping fuel bills down. But your HRV can't do all this without your help.
It only takes seven simple steps to keep your HRV happy…

The Seven Steps to a Happy HRV

First turn off the HRV and unplug it.

• Step 1: Clean or Replace Air Filters
Dirty or clogged filters can lower ventilation efficiency. Try to clean your filters at least every two months. Filters in most new HRVs can be easily removed, cleaned with a vacuum cleaner, then washed with mild soap and water before being replaced. Older units have replaceable filters. If your HRV is easily accessible, this is a 5 minute job.

• Step 2: Check Outdoor Intake and Exhaust Hoods
Remove leaves, waste paper or other obstructions that may be blocking the outside vents of your HRV. Without this vital airflow, your HRV won't function properly. During winter, clear any snow or frost buildup blocking outside vents.

• Step 3: Inspect the Condensate Drain
Check to see if your HRV has a condensate drain, a pipe or plastic tube coming out of the bottom. If it does, slowly pour about two litres of warm, clean water in the drain inside the HRV to make sure it's flowing freely. If there's a backup, clean the drain.

• Step 4: Clean the Heat Exchange Core
Check your HRV owner's manual for instructions on cleaning the heat exchange core. Vacuuming the core and washing it with soap and water will reduce dust which can build up inside the core.

• Step 5: Clean Grilles and Inspect the Ductwork
Once a year, check the ductwork leading to and from your HRV. Remove and inspect the grilles covering the duct ends, then vacuum inside the ducts. If a more thorough cleaning is required, call your service technician.

• Step 6: Service the Fans
Remove the dirt that has accumulated on the blades by gently brushing them. Most new HRVs are designed to run continuously without lubrication, but older models require a few drops of proper motor lubricating oil in a designated oil intake. Check your manual for complete instructions.

• Step 7: Arrange for Annual Servicing
Your HRV should be serviced annually. If you are not comfortable doing it yourself, contact a technician accredited by the Heating, Refrigerating and Air Conditioning Institute of Canada. Make sure the technician you call has been trained by the manufacturer of your HRV.

Check Your HRV Balance: the Garbage Bag Test
HRVs need to be balanced, with the fresh air flow matching the exhaust flow. If you do not know if the HRV was balanced when installed or if you have changed or added HRV ducts, you may want to check the balance with the following simple procedure. This rough test will take about 10 minutes.

Use a large plastic leaf collection bag, typically 1.2m (48 in.) long. Untwist a wire coat hanger. Tape the wire to the mouth of the bag to keep it open. You now have a garbage bag flow tester. Go outside to where your HRV ducts exit the foundation.

• Step 1:
Crush the bag flat and hold the opening tightly over the exhaust hood. The air flowing out of the hood will inflate the bag. Time the inflation. If the bag inflates in eight seconds or more, go to Step 2. If the bag inflates in less than eight seconds, turn the HRV to a lower speed, and repeat the test. Then go to Step 2.

• Step 2:
Swing the bag to inflate it and hold the opening against the wall around the HRV supply hood. The air going into the HRV will now deflate the bag. Time the deflation. If your HRV is balanced, air going into the HRV will balance the air coming out of the HRV. The inflation and deflation times should be roughly equal. If you find that the bag inflates twice as fast as it deflates, for instance, your HRV is unbalanced. If you can see no problem with the filters that would cause such an imbalance, you should call a service person to test and adjust your HRV.

Please don't ignore your HRV. Just a little bit of your time is all it takes to keep it running smoothly.

• April or May
— Turn dehumidistat (the adjustable control on many HRVs which activates the HRV according to relative humidity) to HIGH setting or to OFF.

• September or October
— Clean core
— Check fans
— Check condensate drain
— Check grilles and ducts in house
— Reset humidistat (40%–80%)

They are separate risks . I'm not conflating anything . Assuming that manufacturers no longer produce defective and hazardous goods there remains the matter of the installation .

Elements of structure must , in compliance with fire regulations - resist fire . I have already described that by simply inserting a standard vent outlet into a plasterboard ceiling - that the fire resistance of that floor is totally compromised . In the event of an outbreak of fire the ceiling outlet will melt and the fire will travel rapidly into the floor cavity .

Flashover will occur within minutes to set the very floor structure alight - That same structure that is - in the case of a typical domestic construction - required to resist fire for 30mins . It will not resist for longer than 2 mins .

Smoke and other combustion gases will with great force find in the floor deck over , every crack , loose fit , knot hole and expansion-gap-against-the-wall and quickly intoxicate and then kill anyone on that floor .

So why hasn't anyone reported this ? Surely we would have heard ? Come off it . Why wait for that ?

Again I say - simple solution . Fit fusible link fire outlets .

And co link the motor to power down when fire detection system activates .

But no does this . Because "no one makes us"

http://www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/96215.htm

Canada 1999 - 10 years after HRV first appear there

"In some installations, HRVs may not be realizing their full potential due in part to installation faults and in part to a lack of homeowner understanding. Existing information transfer mechanisms need to be improved. As many of the problems noted in the existing systems could have been prevented by proper installation, installers should be required to pass the installation and designers training programs offered by the HRAI. Installers should also be encouraged to offer HRV maintenance agreements to home owners and/or impress to them the importance of proper operation and maintenance.

The issue of most concern is that of properly balancing HRVs. In one house, the supply fan was not functioning. The homeowners were not aware of the problem because they still heard the sound of the exhaust fan. The result was backdrafting of the fireplace and the potential for backdrafting of other combustion appliances. HRV systems should be installed with balancing dampers and permanently installed flow measuring stations. Also of great concern is that filters were found to be dirty and air intake clogged. Clearly lack of owner appreciation of the potential hazards of a poorly maintained and operated HRV is also an issue of concern. The industry should also be encouraged to develop trouble indicating devices (e.g., trouble lights) or fail safe controls to indicate component failure or overdue maintenance.

Other recommendations for improving HRVs include limiting the use of flexible ductwork or encouraging proper design and installation. Cross-Furnace installations, which are most affected by varying the furnace speed, should also be discouraged. Circulation systems must be in operation to distribute fresh air throughout the house when an extended or simplified system HRV is in operation; controls should be provided with all such systems to allow continuous operation of the furnace fan at a low speed. (Such interlocking is now a requirement of the 1995 National Building Code of Canada.)

In order to improve HRV system performance, the regulatory agencies should continue with the current trend towards greater regulation regarding contractor training and certification standards, and HRV system installation practice and system requirements."

Will history repeat itself this side of the Ocean ?

That guidance relates only to additional measures required for larger domestic properties . Fundamantally -

do not expect to cut a hole in your plasterboard ceiling , fit a pvc item into it , and expect those above to remain safe from fire

and if a fire should start - do not allow your hrv/mvhr system continue to supply it the oxygen it requires to really thrive

Given that other countries, such as Germany, Austria and Switzerland, have greater practical experience of the deployment of MVHRs, has this resulted in regulations or industry codes of best practice that are more stringent than the UK building regulations?

If the ducting for a MVHR crosses floors isn't it more effective to place fire stops at the floor crossings rather than the room outlets as suggested by sinnerboy?