Having worked in a safety-critical industry for over 40 years, the last thing one does is leave procedures etc open to independent interpretation. This is the first step in aligning the holes up in a Swiss cheese.

i confess that I am surprised by the Octopus Energy’s rep’s comment. He has been adamant on a number of occasions that air bricks are not considered to be a R290 gas problem. This view is backed up by the table that I posted above. Is he now saying that air bricks are a constraint?

The technical dept that I contacted was Stiebel-Eltron. They copied me an extract from their installation training manual that rules out air bricks within the protected zone. For confirmation, I sent them a photo of the type of air bricks within installed in my property. The advice did not change.

Yes, I could block up an air brick but as the house is built on clay this is probably not a good idea. A recent foundation survey found water 2 feet down from the soil top on a hot summer’s day. Blocking the air bricks off would breach Building Regulations and probably invalidate the NHBC Warranty.

There is an irony here. Looking at the air brick pattern, an Octopus Cosy HP with its small width and 500mm side protection would just fit in one wall position without compromising safety. I am not that keen on the Cosy given its link to one supplier that may not be in the HP business in 10 year’s time.

Given my age, I was hoping for a minimum disrupt option that a R290 HP offers but I sense that I need to look more carefully at alternative R32 models.

@l8again, I’ve received a lot of feedback on the subject from senior people in the industry. I’ll collate the replies and post them here later today, but it’s rather inconclusive tbh.

Here's the feedback:

Peter Spurway from Viessmann made a comparison that’s worth sitting with. If this were a boiler flue failing clearance distances to an air brick, it would be a complete non-starter. No debate, no risk assessment, no “it’ll probably be fine”. The installer would have to reroute the flue, move the appliance or select a different product. His point was that the same mindset should apply here: the safety zones exist for a reason, and the correct response isn’t to look for special dispensation, but to select a product that suits the property and follow the manufacturer’s instructions to the letter. From a manufacturer’s perspective, once refrigerant leaves the appliance, what happens outside is no longer within their control. which is exactly why exclusion zones exist. 

I'm not sure I agree with the comparison because the flue has an endless supply of fumes... there's only 1kg of propane. My interpretation.

He also made the point that most manufacturers base their guidance on LPG regulations. Some reduce distances, some don’t, but the underlying principle is the same: mass-market safety has to come before “what’s the minimum I can get away with”. Leaving this to installer risk assessments, particularly given the standards we’ve all seen under schemes like ECO, is not a road many manufacturers want to go down.

Chris Johnston echoed this from a slightly different angle. He described the whole topic as a bit of a minefield. In reality, even in a full refrigerant release, the likelihood of propane building up under a suspended floor via air bricks to anywhere near flammable limits is extremely low. But his key point was the same: why would a manufacturer ever want to formally say “that’s fine” and expose themselves to liability? Saying “no openings in the exclusion zone” is simple, clear, and defensible, even if it’s arguably over-cautious.

There was some discussion about mitigation measures. David Brown mentioned hearing that R290 units are being installed alongside gas detection systems. That was quickly challenged by Trevor Clark, who pointed out the practical reality: any leak would occur outside, disperse into ambient air and detectors installed inside the home are vanishingly unlikely to ever see anything. His concern was that this could become expensive theatre rather than meaningful risk reduction.

A few people questioned proportionality more broadly. Mark Griffin, Technical Training Manager at Ideal Heating, highlighted the contrast between the scrutiny applied to R290 heat pumps and the complete lack of regulation around common garden LPG appliances (often connected by homeowners themselves using rubber hose and jubilee clips). Meanwhile, a factory-built, pressure-tested appliance with brazed joints is treated as inherently more dangerous. It’s a fair observation, but it doesn’t change how manufacturers have to write guidance.

On the specifics, Michael Cosham was very clear: any opening (including air bricks and drains) within the typical 1m exclusion zone should be avoided. @sune suggested a practical workaround where possible: repositioning the air brick. Not a solution to the wider inconsistency in interpretation, but sometimes the simplest fix if the building allows it.

Others, like Mark Freeman and Bruce Boucher, questioned whether the whole issue is being overblown, pointing out the small refrigerant charges involved (around 1.3kg in a 10-12kW Vaillant unit) and how fleeting any release would be in open air. Technically, they’re probably right, but again, manufacturers don’t write guidance based on “probably”.

So where does that leave you? Unfortunately, with an uncomfortable but clear conclusion: if a manufacturer’s instructions say no openings within the exclusion zone, then air bricks are a problem for that product.

Your options realistically come down to three things: reposition the air bricks if feasible, choose an R290 unit whose exclusion zone genuinely fits your property or accept that an R32 system may simply be the better fit for this particular building. 

The heat pump industry is still clearly trying to reconcile real UK housing stock with emerging refrigerants like R290, inconsistent guidance and a regulatory framework that hasn’t quite caught up yet.

@jamespa, Thomas Root from Octopus had the following to say about R290 heat pumps and windows: "there’s no issue as long as the window threshold is at or above the highest point of the unit containing R290, as R290 is heavier than air."

I'll see if I can convince Thomas to join the forums.

@editor 

We've not long had this discussion with installers.

Our HP will be sited below a ground floor window and next to 2 drains that manage the waste water from a bathroom sink and the utility room.

Octopus were not happy about the window, so ruled out an R290 unit. British gas weren't worried about the window, but were more concerned with the drains so ruled out an R290. Heat Geek were fine with both so suggested an R290 unit...

This is clearly an area of confusion for installers, let alone us home owners.

In the end we went for an R32 HP and had the radiators upgraded significantly to allow for a low flow temperature, thus avoiding the likelihood we would need a high flow temperature that the R32 HP may struggle with.

Wow - I seem to have wandered into a minefield here. It would seem that the industry is as confused as I am!

There is a further consideration. R32-gassed HPs are all fine and good save for the fact that in the EU they will be banned for new installations below 12kW from 2035.

Surely, this will result in manufacturers moving away from R32 to just R290. It follows that there will be fewer service engineers bothering to F Gas qualify (and I have no idea what that entails) and householders who, in the future, need to replace their R32 HP might find that their existing HP location is unsuitable for a R290 unit.

@l8again Manufacturers will support R32 for quite a long time after they are phased out for repairs, this is evidential on AC brands, by the time R32 is phased out the rules would have changed and you will likely be allowed to place the units by vents and windows as they will deem the rick as marginal, so lets see when this happens.

Why would there be less F-Gas engineers? you need F-Gas for R290 as well to work on the circuit. If you had to change your HP in 15yrs from R32 to R290 or by then what ever the new gas is, it is likely that either the above would have happened locations are less restricted or some other solution will be available. I do understand though it hard to make an informed choice if this is all likelihood rather than confirmed changes.

I am completely out of my depth here as I am sure you can tell.

This is what a search about R290 reveals:

This is the F-Gas part training for A3 (so this qual covers all F-Gas + Hydro carbon add on) you currently cannot only get the A3 hydro carbon without the A1 and A2 so we still call this F-Gas + as there is no way round it without the F-gas tickets this stops people not being F-Gas 

@l8again If you want to site your HP near an air brick and it is a new build house with plastic air bricks you could check building regs to see if you need all the air bricks. 

The standard response to how many air bricks you need is one every 1.5-2 mtrs, or every 6 foot, and that is what bricklayers usually put in, but plastic air bricks have a greater air flow than traditional clay airbricks.  I have ours much further apart as I checked the regs then had a conversation with the building control inspector when we built our house last year and they don't necissarily need to be that close. I have them 2.7 mtrs at their closest point and some are 5 mtrs apart and we still have more than enough airflow under the building to meet the regs

Țhanks @johnnyb. All my air bricks are in the 1.5to 2M category. My Grandson’s partner is a Local Authority Buildings Inspector so I will have a chat with her.

Posted by: @l8again

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My Grandson’s partner is a Local Authority Buildings Inspector so I will have a chat with her.

That sounds like it could be helpful for this.