Jeremy Harris

I think I've said this before here, or maybe on this forums closed predecessor, Ebuild, but it doesn't hurt to repeat it. My view is that forums like this are communities of like minded people, and there are parallels with a group of regulars in a pub. Many here have known each other a long time, several years for some of us. I joined the old Ebuild forum in 2008, and there are a lot of members here who were members of Ebuild from back then, too. That means we all know each other pretty well. When a new member joins, we try to be welcoming, but it does pay for new members to have a think about how they may be perceived by a bunch of people that have known each other for a long time. For example, if someone entered a pub, and started giving the locals unsolicited advice, just because they felt it might be useful, and with no knowledge of the skills and experience of those locals, how do you think it would be received? The advice may well have been given with the very best intentions, but I'll lay money that many of those locals would get their backs up at someone they didn't know telling them stuff that some of them may already be very familiar with. The same applies here to a degree. We have a broad range of members, from university and college lecturers, academics, members of our emergency services, energy assessors, planning and tax experts, IT administrators and systems designers, tradespeople in every aspect of construction, engineers, technologists, serial self builders with a great deal of practical experience, and at least one oddball scientist. Taking the time to understand the nature of this forum, and the very broad range of skills and experience within its membership, before posting anything, is a wise move for any new member. The better we all get to know new members, the more inclined we will be to accept them with open arms into our online community.

That takes me back many years. When living in West Cornwall in the late 70's, I was lucky enough to have the use of a friends boat, a 28ft sloop that he kept on a mooring at Mylor. He worked in Dubai, making concrete staircases for Cornish Concrete Products, and was officially an ex-pat, so subject to the 60 day rule, where he couldn't spend more that 60 days in the UK without getting an income tax bill, He worked 6 weeks on, two weeks off, so had loads of leave that he couldn’t use in the UK. I used to sail his boat, single handed, over to France, so we could have cruising holidays around the French coast, then he'd fly back to Dubai and I'd sail his boat back to Mylor. In return for this, and checking his boat regularly whilst he was away, I had free use of it. It was always stocked with loads of tinned food and the fresh water tanks were always full, as my plan was that as soon as I got the early warning (I was lucky, my job meant I'd probably get a ten minute head start over most people) I'd drive to Mylor and sail off, heading out of the Western approaches and then due south, to get across the equator and into the Southern hemisphere as quickly as the weather would allow. I'd studied the likely fallout pattern, and it seemed clear that the initial fallout and destruction would be largely confined to the Northern hemisphere, I thought that if I could hold out to the Azores, I might be in with a chance of getting some fresh water and maybe supplies, and could then head towards the cape and out into the Pacific, with the aim of trying to land somewhere in the South Sea islands. My girlfriend at the time thought I was completely mad, and constantly moaned about the large ready-bag I kept by the front door. To me it was a very real and present danger, one that was hopelessly trivialised by the Protect and Survive public service announcements and leaflets.

Remember that we are at a severe threat level, an attack is imminent, and the PM is the person under the greatest threat of attack in the country, greater even than the Queen. She was advised by the security services that if she appeared in an open public setting they not only would not be able to guarantee her safety, but that she would be putting members of the public at risk, both from any potential attacker and from the defensive action that the her armed protection team may have had to take. She could have undertaken a controlled access visit, within a safe cordon, as the Queen did, but I rather think that would have attracted more criticism from her detractors (and frankly I don't like the woman, so I'm not defending her here at all).

There is a fair bit of internal monitoring in the ASHP we have, plus an internal alarm in the house that operates when there is a heat pump problem. There seem to be several temperature sensors inside the unit, along with an over-pressure cut out switch in the refrigerant circuit, so I feel reasonably confident that there would be an effective alarm if there was a problem. This probably varies a bit from one manufacturer to another, though. I suppose it's also worth mentioning that we have three other air source heat pumps inside the house, the fridge freezer in the kitchen, the air-to-air heat pump inside the MVHR unit and the small beer fridge in my study..................

I've spent the last half hour or so searching through the data available on RS5000 and FR5000. Celotex mention that FR stands for Fire Resistant on their web site, but they only hint at the differences there may be between the different products. All use the same basic PIR chemistry, it seems, but there seem to be differences in the way the different products are laminated. Celotex aren't very clear, but there are suggestions in their literature that mention the glass fibre layers in the different PIR products, as well as differences in the foil/paper outer coating. Changes to the number of glass fibre layers, or the positioning of these inside, or perhaps on the outside of, the foam, might change the fire resistance, but would not change the flammability. I suspect we may discover more about the exact make up of these products during the investigation, as it seems likely that there will be a focus on the flammability of the whole cladding scheme.

I posted a PIR facade insulation fire resistance test video on the first page of this thread, that illustrates this well:

According to the data for FR ("Fire Resistant") 5000, it is designed to be more fire resistant than their standard PIR. This isn't the surface spread of fire rating, both are Class O, not that that means anything in this application, it seems that FR5000 has a higher resistance to breakdown at high temperatures, so off-gasses more slowly and the spread of fire through the material (not along the surface) is slowed down.

In that case, that's another deviation from the original specification, along with the change from zinc to aluminium cladding, and that raises still more questions. The original spec was definitely for FR5000 with a zinc composite rainscreen, not RS5000. I'm aware of the chemistry difference (my first degree was chemistry)

Ours has a wrap-around heat exchanger at the rear, that draws in air from the side and the rear. Some are circular, and draw air in from all around and expel it from the top. I think the main thing is to leave enough room for air to be able to freely flow into and out of the unit, and there are minimum distances in the installation instructions to allow this. If placing one out in the open, then I think the only thing to be concerned about is the effect of wind. Ideally, the unit needs to be in a fairly sheltered location, away from strong winds, I think. There doesn't seem to be a practical problem with just having them fitted parallel to a wall, spaced away from it by around 500mm, as far as I can tell. The intake area is pretty large, larger than the front elevation area of the unit, because of the wrap-around design, so the intake flow velocity is pretty low. Even the outlet air flow velocity is fairly low.

I can stick the calcs spreadsheet up later, either here or as a download from my website. It was designed to allow me to do some comparisons of retaining wall construction methods, when I was trying to find the best compromise between width and cost, and although it uses the same recognised methods for calculating earth retaining structures that an SE would use, I'd not rely on it as proof that a structure is safe. If the shear key is in undisturbed ground then I'm pretty sure it should be OK. As a general rule, for soil types that have a reasonable max allowable shear stress, the shear key will probably be a bit of an overkill in terms of resistance to sliding, anyway. The base sliding load from a structure like this is going to be fairly low, I think.

As Dave rightly says, the shear key won't do much at all if it's in the sub-base. To work it needs to be in compacted and undisturbed soil, with shear properties that have been used in the sliding stress calculations that were a part of the retaining calcs. I have a spreadsheet to do gravity wall calcs on my main PC, so could run some numbers and see what it looks like later. To do this I'd need all the base data on loads, soil type and bearing/shear stress, any surcharge from structures or imposed loads higher up the retained area, etc.

Which is precisely why I posted this facade fire test video of PIR earlier in this thread, to demonstrate exactly this point: Also, the product used was FR5000, the more fire resistant form of Celotex PIR, not the slightly more flammable RS5000, as I mentioned in this post earlier in this thread:

Which is precisely why I wrote this:

The foam wasn't PUR, apparently, it was Celotex FR5000 PIR, so a bit less flammable, but still a source of flammable gasses as it broke down under heat. From the photos, it looks like a lot of the charred PIR is still on the building, which suggests that the foam wasn't the primary fuel for the fire. Also, looking at the flames when the tower was alight, there are clear signs that a lot of the external fire was probably the aluminium itself burning. As aluminium burns at a very high temperature, there probably aren't that many materials that could have withstood the heat. I'm surprised that there seems to be so much charred PIR left, but that may well be because most of the photos that show enough detail are of the lower levels, where the temperature may well have been a lot lower, due to the incoming fresh air updraft. Apparently the new windows all had PVC cills and surrounds, and this may well have been the initial fuel that fed the cladding fire: http://web.archive.org/web/20161223144358/http://www.kctmo.org.uk/sub/assets-and-regeneration/153/grenfell-tower-q-and-as-windows-and-heating

A quick look inside ours shows that it is mainly of metal construction, with some neoprene pipe insulation, a plastic fan and a flammable refrigerant gas. There are no heat sources inside the case, and no flammable materials adjacent to the circuit board that I can see. The only real fuel source within the unit seems to be the refrigerant, and a refrigerant leak will trigger the low primary circuit alarm and turn the unit off. Frankly, I suspect that heat pumps are a pretty low risk, as long as they don't contain either heating elements, flammable material in the case and structure, or flammable insulation. Some certainly do have electric heating elements, both to assist during defrost and as flow temperature boosters, and these may pose a greater risk. As @dogman rightly says, there is a requirement to space them away from walls so that they can get a good intake air supply, and this, combined with the fact that the fan blows outwards, away from the building, should reduce the risk a lot.

Therein lies the major problem! Fire resistance testing involves one of several different ignition methods, depending on the product and its intended use. It's unlikely that a product intended solely for external cladding would be subject to the same ignition source when being tested as a product more widely used, say as interior wall cladding in a public space. In addition, some materials are not tested at all, but achieve a classification based on historical safe use. Metal cladding is one such example, I believe. Whether a composite cladding panel is treated as the much greater fire risk that it is, I don't know., but, given all the skulduggery that surrounds self-assessment and testing for product approvals, it wouldn't surprise me at all to find that some approval elements had been read over from other sheet metal products.

The bottom line is that the media can't be bothered to fact-check, in their haste to sell a story, social media is just very fast and wide-spread gossip, and mainly entertainment, not a source of facts and the only way to find out anything that approximates to the truth is to spend a lot of time filtering out the false information, outright lies and misunderstandings that fill a large part of the information resources we have access to. As a side point, one of my frustrations with trying to find facts stems from the inherent advert-related bias and promotion of paid-for stories that dominates all internet search engines. The majority of the stuff that turns up from a quick search seems to be false or misleading, something that probably doesn't help anyone who may be trying to produce an accurate media story.

The specification for the building lists it as FR5000, manufactured by Celotex. This is a PIR foam with a suitable spread of surface fire rating, but it is not wholly fire resistant, and like all PIR (see the test video I posted earlier in this thread) it will burn under conditions where there is a high temperature ignition source plus an abundance of oxygen, from the chimney effect up the cavity behind the rain screen. There is a great deal of inaccurate media reporting, they are far too lazy and incompetent to fact-check, and when I tried to correct an error in a report yesterday I had a very condescending reply by email.

I think it's also worth noting that the original architects drawings show that the rain screen cladding is zinc composite panels, not aluminium. It seems that at some point, a decision was made to switch from the more fire resistant zinc panels to cheaper aluminium panels. One wonders who made that decision, and whether the impact of it on external flammability, was taken into account.

I've seen that too. It seems the big companies involved in this refurbishment are trying hard to deflect blame from themselves onto the regulations. That may work in the court of public opinion, but in law they have a responsibility for safety that extends beyond the remit of building regulations compliance. As some know, I've been involved, as a witness, in what used to be called gross negligence manslaughter. The law is clear, and responsibility is not limited to compliance with regulations at all.

I think we, as a group, are almost certainly better informed than anyone in the media, and probably most in government. Some of us have looked at the use of external insulation and cladding in depth, and have studied some of the issues that need to be resolved in order to make it a practical proposition. Some of us are aware of the fairly long history of facade fires that have been facilitated by EWI and cladding systems. Inevitably we're more likely, as a group, to be more analytical of the factors that contributed to this tragic fire than most in the media. I've been trying, over the past 24 hours, to feed the media with old internet discussions about EWI and fire risk, yet it seems that none have the interest or patience to read through the stories of the many previous instances of facade fires, together with all the information the the BRE has published, together with fire test videos on YouTube, about the facade fire risk.

As some here know, I've been an open critic of the gross failings in the building inspection system for large construction companies for some years, ever since I first discovered the disparity between the way self-builders projects were inspected and the seemingly lax approach taken on new developments, where there are many, many, examples of new builds and refurbishments failing to comply with even basic building regulations, yet being signed off. I watched a harrowing news item last night, a young man, telling how he had stayed on the phone to his brother, who was trapped in one of the flats, for two hours. Their conversation ended when his brother stopped talking, probably overcome by smoke. There was a similar story from the family of another person trapped in a flat. I cannot begin to imagine what it must have been like, trapped for hours and knowing that you were likely to die in your own home, powerless to do anything to save your life. I've always felt strongly about the way the construction industry has been able to ignore building regulations, and the ineffectiveness of the building inspection system. Friends here will remember that I have quoted before that a building inspector told me a couple of years ago that he felt that around 60% of new builds failed to comply with the building regulations. Right now I feel bloody angry and frustrated that it has taken a major tragedy to get people to wake up to what's been going on for many years.

FWIW, I've found that the pump in our re-badged Carrier is a standard variable speed circulating pump. Our pipe runs are short, less than a metre of 22mm copper, plus 900mm 19mm bore flexible pipes at the ASHP itself. I had to turn the pump in the ASHP down to its lowest setting, as the flow was far too powerful with it on setting 3. Given that the pump looks to be a standard unit, it may well be possible to substitute a larger one if needed. The only things inside the ASHP on the water side, apart from the pump, are a standard looking plate heat exchanger, a tiny expansion vessel, a drain cock and an air vent. All except the plate heat exchanger could be removed and replaced pretty easily, I think.

@Grosey I didn't keep count of the number of casual snoopers we had around the site, but it was around ten or twelve I think. Sadly we didn't have any as entertaining at those in your first shot..................

I think it's worth putting domestic fire risk into context with a major fire like the Grenfell House tragedy. The risk in any large building, with many occupants, is massively greater than that in a single dwelling, for several different reasons: - A fire started in any one of the 120 flats in the building has the potential to kill and injure hundreds of people, so the risk factor is raised because of this. - Most of the occupants have no control at all over fire safety, they have to rely on the systems in the building and the safety consciousness of their neighbours. - Fires in single dwelling rarely attack from outside, as this fire did, they are almost always from a source inside the dwelling itself. - The flammability of the outside of a single dwelling is only really a minor risk factor, as there isn't likely to be an ignition source outside. So, as long as we have well-designed fire alarm systems, and have adequate protection from fire and smoke for the time needed to get out of the house, then we should be safe enough. It's worth watching the half hour video I posted earlier in this thread, as that shows firefighters walking around inside the building, when the fire had been burning on the outside for around an hour. An hour is a very long time during a single dwelling fire, far longer than is needed to get out. One lesson we can learn from this fire is that the means of escape from fire that we provide needs to be better than the building regs require, if we can make it so. Interestingly, the house I grew up in was a 1920's built two storey house, with a veranda and balcony running along the rear elevation. The bedrooms on that side of the house, including mine, had French windows on to the balcony, and at one side of it there was a wooden box with a chain fire escape ladder. That wouldn't be required under current building regulations, which may give pause for thought. As an aside, as a teenager I found that ladder invaluable for sneaking out and back late at night, without my parents knowing................