Posted by: @jamespa

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Posted by: @toodles

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@heacol Sorry Brendon, but there is no ‘should be’ about it! The temperatures in my house are what I desire them to be, I live in it, not an advisory body like MCS! Regards, Toodles.

resistance is useless! 

😆

No it's not; resistance creates heat, which could be very useful....

Sorry, I'll get my coat.

Posted by: @toodles

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@heacol Sorry Brendon, but there is no ‘should be’ about it! The temperatures in my house are what I desire them to be, I live in it, not an advisory body like MCS! Regards, Toodles.

@majordennisbloodnok Everything we do is about assumptions, we do not have x-ray eyes that will expose the failures of the building industry, so accurate modeling can be done. There is no way to supply 100% accurate heat loss calculations, even thermal imaging, in-situ testing, and historic data involve guesswork and assumptions to achieve a result.  In reality, any heat-loss calculation is at best an educated guess that requires significant experience to achieve any form of reasonable accuracy. Most commercial calculators overestimate the requirements by 20-30% to cover for this. The reason that majority of heat pumps in this country are oversized. I do not use commercially available heat loss calculators and have developed my own which has been honed over the last 15 years with great success.

@heacol Fair comment as you have not seen the house but it is a kitchen/diner there is no door to the hall/landing and we keep the doors to the lounge open as well.

Posted by: @heacol

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@majordennisbloodnok Everything we do is about assumptions, we do not have x-ray eyes that will expose the failures of the building industry, so accurate modeling can be done. There is no way to supply 100% accurate heat loss calculations, even thermal imaging, in-situ testing, and historic data involve guesswork and assumptions to achieve a result.  In reality, any heat-loss calculation is at best an educated guess that requires significant experience to achieve any form of reasonable accuracy. Most commercial calculators overestimate the requirements by 20-30% to cover for this. The reason that majority of heat pumps in this country are oversized. I do not use commercially available heat loss calculators and have developed my own which has been honed over the last 15 years with great success.

@heacol, I'm not trying to be combative but there's an important point being made here.

I disagree that everything you do is about assumptions; a heat loss survey, for instance, is based on measurement first with assumption only filling in the gaps that cannot reasonably be measured. The point - that I was very careful to make in my previous post - is that you do not need x-ray eyes, thermal imaging, in-situ testing or historic data to:

1. make a visual note of whether or not a kitchen does indeed contain equipment that can significantly add to the heat in the room
2. ask a customer what temperature range they'd like to have in their kitchen (or bathroom, or bedroom etc.)

One of the forum members (@iantelescope) stated in one of their posts that they had a medical condition requiring their home to be above a particular temperature, and I have little doubt there are other forum members in broadly similar positions. Surely those requests ought to be listened to rather than merely designing a standard relatively low temperature for the kitchen on the assumption some of the domestic appliances there will make up the shortfall? A medical condition, after all, is not just a fussy customer and the assumptions being made are very easy to verify or disprove.

If your own heat loss calculations have met with significant success I would guess you're already amending the balance of assumption vs evidence-based fact in favour of less guesswork which is, after all, the only thing I'm suggesting should be done. I'm also guessing that your comment of "18 degrees C is the temperature kitchens should be designed to" was actually a shorthand generalisation standing in for a rather more lengthy set of criteria for taking into account the unique circumstances of that kind of room. If I'm right in that, I'm disagreeing with what you said whilst agreeing with what you meant to say. After all, I'm an expert in being a customer, not an expert in installing heating systems.

@heacol And how many of those 900 pumps have you lived with through a full winter please? Regards, Toodles.

Since we are talking about assumptions here, can I carry across the essence of the discussion going on in another thread which is - why don't we use measured (usually gas) consumption and known or available data about the weather, to get a handle on whole house heat loss to complement/sense check/replace the spreadsheet method.  The latter, certainly in a retrofit, pretty much requires that assumptions are made about the fabric that can be wildly adrift.

Half hourly meter readings contain a wealth of data that we currently ignore for reasons that, to be honest, escape me.

Of course this would still need some me corrections, but I would suggest that they are either less uncertain or of a smaller magnitude in the majority of cases than trying to guess the fabric.

I'd be interested to hear the view of @heacol on this, or perhaps he has a better method still  that is better as @majordennisbloodnok suggests.

@jamespa It’s seems stupid to ignore all that excellent data which at least compliments other methods and may in fact be more accurate. Protons for Breakfast is an excellent information source if anyone on here hasn’t already seen it.

Posted by: @bontwoody

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@jamespa It’s seems stupid to ignore all that excellent data which at least compliments other methods and may in fact be more accurate. Protons for Breakfast is an excellent information source if anyone on here hasn’t already seen it.

Well I agree of course, Im hoping @heacol (or someone else from the industry) will comment!

Posted by: @bontwoody

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@jamespa It’s seems stupid to ignore all that excellent data which at least compliments other methods and may in fact be more accurate. Protons for Breakfast is an excellent information source if anyone on here hasn’t already seen it.

As discussed on another thread you could get in a situation where it's rubbish in and rubbish out. You need comparative data in all circumstances, the boiler needs to run in like for like mode, as the ASHP for a prolonged period - most cannot do that. My gas boiler as installed used 100% more gas than the design calcs predicted, once optimised, running full WC with 1 zone, it performed as expected, my heat pump does also. Like for like conditions is ok.

You taking my money and everyone else's money via a grant, you may want a house at 16 degrees, but the next owner of your house may be wants a more constant 21. I certainly wouldn't be happy if I purchased a house with a grant funded heat pump installed, that was undersized and ran an immersion to keep up when it was little cold outside. Your gas consumption data is of little use generally. Suspect 99% of the general public have not even heard of weather compensation or understand you can run house with no thermostats. Many on forums like this, don't really believe it.

MCS isn't perfect, if you don't like it don't take the £7500, self fund - just like I did. Then you are free to do as you wish.

@jamespa There are many theories that may or may not help with heat loss, however, in reality, in a new build property, it is irrelevant as 80-85% of the actual heat loss is ventilation, which is the greatest elephant in the room and very fairly delt with. In addition to that, the insulating properties, of any insulating material follow the laws of diminishing returns. 75mm of any insulation gives 90% of its insulating value, the next 25mm gives another 5% and a further 100mm gives another 1%, and so on. The 2 big cons in the building trade ventilation and insulation.

In reality, when doing heat loss on a new build, (from 1980 onwards) unless it was a self-build and you speak to the builder, the heat loss assumptions are always worst case scenario due to the terrible building standard in this country. Prior to that, the properties were generally built by craftsman, and you know exactly what you get. It is much easier to get an accurate heat loss in a building built prior to 1920, because you know exactly what you are getting, there are no surprises.

@JamesPa, I agree, but what is the efficiency of the boiler? Ofgem have found a variance from below 50% to above 90%, using the gas usage as a metric, like any metric, is only of value if all the variables are known or quantifiable. As we have no idea what the efficiency of the existing boiler is, is it of any use?

@majordennisbloodnok To get the grant and comply with permitted development, we as installers and designers have to design to at least BS EN 12831:2003. Below are the templates we have to design to. If the customer asks to have a higher temperature, that is permitted.

 In a nutshell, the success of a heat loss calculation lies with the experience and intuition of the person conducting the survey and the informed, or ill-informed decisions they make. It has very little to do with the software or anything else. I certainly have not come across any method in the 15 years I have been doing it to make it any easier or more accurate. My calculator is very simple, only 4 wall types, 1 window type, 2 floors, and 3 roof types. It produces lower heat loss requirements that any other commercial one, and complies with BS EN 12831:2003, but in over 900 installations, I do not have a cold customer and an average SCOP of between 4 and 5.

@toodles Perhaps BG screen all their potential customers for conformity to a specified norm before agreeing to install 😆