How to measure real home energy rating ? i.e Not EPC guesswork

Buzby
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How can I measure home efficiency ?. ( I know I have, and can get another, EPC rating, but I’ve not got much trust in them. )

However, I have got thermometer gadgets around the house. These record every 5 minutes to a database somewhere. I can then view graphs going back upto a year.

Using these I can see how, say, the livingroom temperature drops when the CH turns off, or rises as the sun shines in. I am sure that the rate of change could be useful, somehow.

I’m sure I’ve got enough data to actually calculate something useful, but I haven’t got a clue how to do it.

Probably it needs room volumes, wall and windows areas, etc., as well as the records of temperatures.

Does anyone know of a website or app that can take all this info and generate something useful ?

Or, failing that, point me to the required calculations so I can program an Excel thingy myself ?

Cheers,

Buzby

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )

19 replies

ChristopherS_OVO
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Hi @Buzby,

 

It sounds like you’re on a journey of self-discovery around your home efficiency. 

 

As someone who bought a hive system later last year and has been using it for a while now, I often question the accuracy of the internal thermometer. Have you faced any issues with the accuracy of your tech so far, or are you happy with the information they are producing? 

 

Keep us updated on your findings! 

 

Thanks,

Chris

 

Buzby
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Hi @Buzby,

... I often question the accuracy of the internal thermometer. Have you faced any issues with the accuracy of your tech so far ...

 

I put all the thermometers next to each other in the same room, left them for an hour or two, and they all showed 19.6’C, +/- 0.1’C.

So they all show the same value, but I can’t tell if that is the actual temperature without a known accurate reference. However, it is not actual temperature that matters when measuring home efficiency, it’s rate of change.

The gas usage I can see online ( that’s not OVO ), and I know what times the CH is active. I can see the temperature stabilise when the heating is on, and measure the rate of fall when it goes off. I can put the thermometers in any room, even in the attic.

We have fairly recent cavity wall insulation, but rather old and crappy loft insulation. I am going to try and measure the heat loss through the attic. I want to see if it’s really worth spending money, or is the crappy stuff still doing a reasonable job.

Another interesting twist to these calculations is the effect of humans. A human body radiates beween 80 to 120 watts, a not insignificant source of background heating !

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
waltyboy
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Hi @Buzby, have you checked out Glowmarkt.com site? They have lots of info about, for example, one’s Building Fabric Score (“Heat Transfer Coefficient”), a measure of how quickly your home loses 1 degree C in cold weather.  Is this close to what you’re after? I’m not sure how much of their algorithm is do-able using one’s own temperature (and preferably humidity?) sensors, but IIRC their website has good info on how THEY do assess things, they might have some useful pointers…

 

It’s something I’d like to follow up on next winter (can only be really assessed in winter, obvs!), which is one reason I’ve recently invested in their Glow IHD which is supposed to make such an assessment easier, linking their own temperature and humidity sensor(s) at a further cost! I think they can use data from an existing household smart thermostat, but I’m not sure…also not sure about total costs, for example whether they use a “partner” to arrive at a final assessment

 

Hope their site is worth a look for you, at any rate, good luck with it, it’s definitely something we could all be thinking about.

Walt. 2013 installation 3.2kW PV East/West + Fronius IG, >23MWh (18MWh exported). 2023 2.4kWh LiFePo4 battery
waltyboy
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Oh, and see the recent blog article from @hydrosam in this forum titled 

Correctly sizing Air Source Heat Pumps (ASHP) - Bigger is not always better

 

which has lots of relevance and interesting input from many forum contributors, pertinent to your quest to measure your home (heating) efficiency.

Walt. 2013 installation 3.2kW PV East/West + Fronius IG, >23MWh (18MWh exported). 2023 2.4kWh LiFePo4 battery
Buzby
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I’ve just downloaded the Bright app from Glowmarkt.com, and can now see my electricity trend. This what I’m still trying to get from OVO !.

I’ll check the gas trend against the online one from my gas supplier ( who will soon be my electricity supplier if OVO don’t pull their finger out. )

The website also lets me download the logs as .csv, so it will be easy to make some Excel charts. When I work out how to do the same with my thermometers I will have just about all the raw data I need. All will need then is the knowledge to convert data into meaningful info !

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
B
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Other topics that might be of interest to you

https://forum.ovoenergy.com/my-smart-home-138/estimating-heat-pump-or-boiler-size-using-usage-data-and-temperature-17050

and

https://forum.ovoenergy.com/my-smart-home-138/comparison-of-heating-sizing-methods-simple-to-complex-17156

 

ChristopherS_OVO
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Hi @Buzby ,

 

I found this article which I think would help you with making the calculations that you are looking for - https://forum.ovoenergy.com/my-smart-home-138/graphing-your-energy-usage-in-excel-charts-or-similar-by-converting-usage-data-into-a-csv-format-17127?tid=17127&fid=138

 

I hope this helps you!

 

juliamc
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A couple more bits of reading for you @Buzby https://buildpass.co.uk/blog/10-top-tips-for-passing-your-sap-assessment/ and re ventilation/air tightness https://www.bpcventilation.com/blog/nearly-zero-energy-buildings/

I’ve just had a single room MVHR unit installed in my bathroom - the idea being that heat is recovered from the steamy air drawn over a heat exchanger, then fresh air is brought in having been warmed using that heat. https://www.envirovent.com/products/heat-recovery-ventilation-mvhr/heatsava/

My house was chosen for the Electrification of Heat trial run by OVO for BEIS - to examine retrofitting heat pumps in various types of properties. The first stage of that was to get a Whole House Plan to survey all the fabric of the property and come up with a series of steps which would improve the energy usage overall, like a giant EPC but with suggestions ! One of the things identified was to improve the ventilation but of course that would mean a certain amount of heat loss. A full MVHR would have been pointless as the house os no way airtight enough, this single room unit seemed like a good compromise, along with trickle vents in the double glazing.

It’s only been in for a couple of days, it’s on all the time and it’s a bit noisy, when the shower is on it ramps up to noticeably noisy, but we’re getting used to it. There is breeze coming from it but the room temperature is stable, so we don’t appear to be losing any heat. Result !

Buzby
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Interesting reading, thanks !.

Regarding MVHR in your bathroom. How much energy is recovered from the air compared to how much goes down the plughole ?.  Hot water contains a lot of energy !. Same goes for the washing machine and dishwasher, both heat water then throw it down the drain.

Our house is a 1960’s semi, not designed to be energy efficient. We’ve got cavity wall insulation, double glazing, and dubious loft insulation. I’m trying to find if the loft insulation is doing it’s job, but it’s going to be a tricky task.

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
waltyboy
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Hi @Buzby, if you didn’t want to get into the whole HTC measurement thing with the likes of, say, Glowmarkt sensor kit, there are quite a few freestanding temp and humidity data loggers available for around £20 upwards. One is the “Inkbird” Bluetooth, available online for £24, whose  promises include the following

Reliable Logging with Graphs and Statistics】Data record interval can be adjustable(10s、30s、1min、2min、5min、10min、30min) and data is updated at 10-minute interval by default, about 200 days of data can be saved. Refresh a group of data every 10 minutes. Record temperature data via graph or bar graph and Logs can easily be exported as a CSV file by email

 

Can’t vouch for it, I’m afraid, no idea how good it is, but that tempting price caught my eye! It may well be OK to experiment with and stick up in the loft to see how it goes?! 

Walt. 2013 installation 3.2kW PV East/West + Fronius IG, >23MWh (18MWh exported). 2023 2.4kWh LiFePo4 battery
juliamc
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I would say get the loft insulation to 300mm deep, though not burying heavy load electricity cables of course. That’s another ventilation minefield though.

I put the bath plug in while showering to at least keep the heat in the vicinity, rather than waste it straight down the drain. There are fancy contraptions that send the waste water around something to preheat the input to the hot water system somehow. Struck me as a bit over-engineered.

Envirovent reckon the Heatsava recovers 75% of the heat, which is far better than just losing it all through an open window of course.

Buzby
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Here is one of the problems about setting up a monitoring system, which is the right one ?.

The one I’ve gone for is SwitchBot. I only buy them when there’s an Amazon sale, last ones were £13 each.

Once I’ve got a thermometer in all the right places, I then need to find out how to get all the measurements into one computer at the same time.

I think I need to join the SwitchBot forum !.

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
Buzby
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I did join the SwitchBot forum !.

I think I’m the only one there ☹️

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
waltyboy
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Hi @Buzby, not such quick responders, then, as some on the OVO forum?! 
 

Let us know how you get on with syncing your thermometers and managing the data…interesting project…

Walt. 2013 installation 3.2kW PV East/West + Fronius IG, >23MWh (18MWh exported). 2023 2.4kWh LiFePo4 battery
Buzby
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I had a reply from SwitchBot. They do not have any PC based solutions, it’s all phone apps. They do have an API, but that needs the devices to be connected to the Cloud, and I don’t want that.

However, I did find a YouTube video where a guy programmed an RPi to directly read the devices using BLE. That looks promising, no Hub or Cloud involved.

I’ve already got an RPi ( somewhere ), so I just need to find the video again, find some time, and learn RPi stuff.

I will keep you informed of progress, but don’t hold your breath !.

Cheers,

Buzby

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
Tim_OVO
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This is turning into a good discussion, thanks for starting it, @Buzby. Keep us updated on SwitchBot and we’ll convert this topic into a discussion dedicated to that which others might find helpful. 

Carbon neutral - we need a community to get there! My green tech: Aclara SGM 1411-B smart meter, Chameleon IHD6
waltyboy
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Hi @Buzby with specific regard to Raspberry pi linked to energy monitoring sensors I wonder whether you’ve seen the thread on this forum from a year or so back

Energy monitoring - going beyond smart meters…

posted by @Simon1D, with fascinating exchanges largely between him and @Transparent as well as @Tim_OVO and others.  A lot of it is very technical, way above my pay grade! But it is based around RPi (Model-3 I think?), and as one of the posts says, the energy monitoring design as envisaged aims to address such points as these:

 

the proportion of renewable energy at any given point in time

showing which devices are consuming most electricity in the home

getting some idea of whether it’s viable to increase the level of insulation

considering changes to the way you heat the home in future

 

which sound right up your street?  Hope it’s of relevance to you….

Walt. 2013 installation 3.2kW PV East/West + Fronius IG, >23MWh (18MWh exported). 2023 2.4kWh LiFePo4 battery
Buzby
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I’m moving forward !

The YouTube vid is a bit old. When I went to GitHub to find the script, there is a message there saying the script is no longer needed, as the Home Automation platform now incudes SwitchBot directly via BLE.

Home Automation is something I’d heard of, but had never really considered, as it just seemed to be ‘Turn on kettle when I get home’ type of stuff.

But looking at it a bit more, it can do graphs with upto eight traces, so it’s worth a look.

Luckily my RPi is just about big enough to run HA, so I won’t need to spend money on a new one, and HA is free. It looks like a possible solution to Part 1 of my project.

Cheers,

Buzby

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )
Buzby
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I took a long time to get this RPi running Home Automation. Don’t believe any of the hype about how easy it is !.

The HA system automatically finds all the Switchbot thermometers that are in range. ( It also found my televisions, radios, BT speakers, and printers ! ) I have not yet found a location for the RPi where it can see all the thermometers, I might need to rethink my strategy.

The 8-channel graph that caught my attention is not as clever as it looks. It can’t view a historic window, only the latest values. I might need to delve into the HA config to change that.

However, it’s a step forward !.

 

First attempt at multi-variable graph in HA


 

 

 

 

I burn gas, petrol, and diesel. I am 100% Carbon Neutral ( Well, I will be, when I can buy some carbon offsets.. )

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