Comparing Christmas in 2 very different homes

Happy New Year to you all, we hope you had a great Christmas break. Since we got back to work some of us here at Purr Towers have been looking at the results of a little experiment we set up over the break. At Christmas Hermione spent her time in an 18th century folly in North Yorkshire (DP) and I (Liz Stevens) spent it in my parents 70’s build house on the south coast (CC). We thought it might be interesting to take a look at how the 2 buildings behaved with all the family piling in and a roast dinner in the oven.



DP – The 18th century folly is a sprawling 2 story house with 6 bedrooms, single glazed, not insulated, 4 external doors, oil central heating, open fires and a large aga in the kitchen. 8 people stayed in the house over the Christmas period.






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CC – This is a 70’s build box shaped house with double glazing, cavity wall insulation, a very well insulated roof, 4 bedrooms, 2 external doors, a partly integrated garage and gas central heating. 4 people stayed here over night during the period and there were 9 people in the house during the day on Christmas day.





Cooking the Christmas dinner:

DP has an Aga which is constantly running at least at a low level where as CC has a conventional gas oven. The kitchen at DP is a large room with a dining table that seats 8 people, we can see that the cooking of the roast dinner doesn’t have much impact on the temperature in this room as the heat is dissipating and there is no clear time when the oven is working.

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CC has a conventional gas oven so you can clearly see when the oven is turned on (11am). The kitchen at CC doesn’t have any radiators which means it can get quite cold on a normal day but it was constantly warm with all of the cooking and people coming and going. You can also see the oven heating up the room on Christmas Eve while a ham is being roasted.

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Eating our Christmas dinner:

You might have already guessed that DP was rather colder than CC with one of the rooms hardly getting above 16 degrees over the period we monitored despite being heated by a radiator. It’s a very large room, which doesn’t get much daylight, with single glazed windows and a stone floor. This was actually the room where they had their Christmas dinner and the temperature peaked just below 17 degrees – ouch chilly.

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It makes a very interesting comparison to CC where our lunch time temperature was about 22 degrees and the temperature didn’t drop below 20 degrees for the whole period. You can see the difference when you have a well heated well insulated modern carpeted dining room.

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CC conclusions:

We looked to see what was going on with the temperature quite a bit over the Christmas period and there were a few things that surprised us about the findings. I found that I was only comfortable when the temperature was below 22 degrees, once the temperature climbed above this I felt like I was in a tropical jungle. Clearly other people didn’t always agree but it was interesting to know my threshold. We have always know that the downstairs bathroom (Kitten 29) was always rather cold but we didn’t really quite how bad it was and we had no idea that they temperature in the hall by the front door (Kitten 32) was so low. You can see from the Hotspotter view here that they spent rather a lot of the Christmas period below 18 degrees although it wasn’t surprising to see the kitchen (Kitten 13) above 25 degrees for 28% of the time.

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You can also see how the temperature changed from Saturday till Monday:



DP conclusions:

Well we already knew that it was going to be colder at DP over Christmas as it’s further north (so colder outside) and it’s an old building with a few poorly insulated slightly more modern extensions. I think we were all a little shocked at just how cold the dining room was but this room isn’t often used as there is a large dining room in the cosy kitchen not far from the Aga. It’s a big house and it’s going to take more heating than the average building even in warmer parts of the year. I think I for one might have been more comfortable with the temperatures at DP but it really does show us that comfort levels are very personal to everyone. The Hotspotter view below is very interesting and really shows you how cold the downstairs of DP was over Christmas, I’m sure there were lots of cosy Christmas jumpers being worn (I didn’t get to wear mine once at CC!). The dining room is Kitten 48 and the kitchen is Kitten 46 but I’m sure you could have guessed that.

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You can also see how the temperature changed from Saturday till Monday:


If you want to learn a little bit more about how you could use our system in your home, workshop, office or data centre please contact us via email on or call us 01223 967301

Baking with your own data – Import views

If you’re analysing the performance of your building and its HVAC systems you probably already have data from other sources – meter data, building management system data, occupancy data, for example.

We at PurrTowers have been working for a while on ways to allow you to use other data alongside your kitten data. So we’d like to introduce our Data Import view.


The Import view is available if you have an unlimited account (ie any tier above the free account). It allows bulk import of historical data, and attaches the data to a special external-data kitten. This kitten can be dragged and added to other views exactly as if it were one of our own sensor kittens and you can put this data alongside that collected by kittens.

How do I get my data in?

First create an import view as any other by clicking on the Import view in the Create Views selection:


This will create a new Import view:

Import view

Data formats

Data is added to the import by dragging a data file to this view. The data file is going to get analysed before it gets imported to your account, so it helps to get it into the right format. Each line needs to include a time and date, and a value, with a comma between the two:


This can be created using Microsoft Excel by saving a spreadsheet with two columns, one for the date time and one for the value, as a .CSV, comma separated value file. In order to get the date and time format right you’ll need to use a custom cell format which can be found in the cell format dialog box:

dd/mm/yyyy hh:mm

(For some Excel users you may find that this format doesn’t exist, but this link explains how to create the custom format you need)


OK, so you’ve got your data file sorted out, now drop it onto the Import view. This should put it to work, first uploading the file, and then checking the contents:

Analysing ….Found

Organising your Import Views

If everything went well then that Import view should tell you what it thinks of your data, and offer an import button that you need to press in order to get the data in. Once there just use the new Import kitten just as you would any other (yes, you can rename it just as you can rename the Import view).

We strongly recommend that you keep all your Import views in a dedicated project. This makes it easier to find each Import view when you want to add more data.

You can delete the Import view, it won’t delete the kitten or the data that you’ve already imported, you just won’t be able to add any more data to the kitten.

The small print – some important details

OK, as you might expect there’s a little small print:

You need one Import view for each thing that you want to import data for. Example: if you have three thermostats in a room you will need three Import views.

The Import view should happily eat several 100,000 points in one swallow. We have limited the import to 2MByte files at a time.

You can reuse an Import view as many times as you like, adding data from different times to the Import kitten to build up a complete history.

Sorry, but no, we haven’t worked out how to let you delete the data you’ve just imported. Please be careful to be sure that you are adding the data you actually want.

Yes, you can add data that might overlap the data that you’ve already imported. Our far-to-clever for its own good database will just average the data during those overlapping periods.

The Import view needs you to give it data points in time order. If you try to import data that is all backwards, or where some points are in backwards order then it will do its best but it will reject those points.

If the Import view cannot understand your data file it will warn you and let you try submitting different data:



And finally – how much will it cost? We will charge the same amount for an import view as for any other kitten, so depending on the number of end points you are measuring prices will start at £10 per end point, per annum.

This is a new view that will be in beta for the next month so we welcome feedback and bug reports. Enjoy!

Heatmap of the month – cross sections, not cross colleagues

This months heat map is a bit of rarity – an example of what happens when you get HVAC right.

To get this impressive cross section of a London office our customers hung kittens on strings at several points along the ceiling. Each string had a number of kittens, spaced a meter apart, to give a vertical grid of temperature sensors.

The office is a converted Victorian industrial building, with a first floor and mezzanine. It houses about 80 employees for a professional services company, and keeps them at the right temperature with a comfort cooling system that delivers cold air through ducts at floor level.

So what are we looking at here? This is three days from July where the external temperature varied from 9°c to 25°c. Even though this office has a huge volume of open space and floor to ceiling in excess of 8 meters, the temperature on the first floor and mezzanine is well controlled. The mezzanine is a degree or two warmer, but rarely gets outside the comfort band.

Just to be controversial we’ve included a Saturday – and a hot one! – when the comfort cooling isn’t operating, to show the huge heat gain that comes through the ceiling and particularly the skylight along the roof ridge. This poses a big challenge for the cooling system at the higher level.

Looking at the view across the desks on the mezzanine for the same period confirms how well the cooling does at keeping employees warm – providing they don’t get too tall.

Is your cooling doing its job? Or do you have a concerns about where your heating ends up? Let us know about your most perplexing HVAC challenge and we’ll help you diagnose what is going on.

Interning at Purr – Doing ‘all of the things’.

<We’ve had some great people come and do internships at Purrmetrix. Say hello to Fiona, our latest colleague, who’s agreed to answer a few some questions about her work experience here.>

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I’m Fiona, a sixth form student in Cambridge currently in the midst of applying to study engineering at university, and, for the last two weeks, a work experience intern at Purrmetrix.

What is all that fiddling with PCBs you’ve been doing?

All of the things!

Screen Shot 2016-09-06 at 11.38.07Over the last two weeks, I’ve got forty-eight gateways ready to go – this involves a small amount of soldering on each one, cleaning the components on the PCB, fitting the antenna, and installing the whole setup into the case. Once this part is complete, I’ve had help to find each individual gateway on the system so that I can get the correct passphrase for it printed out and stuck onto the case, along with the serial number. Finally, each gateway gets plugged in (only using one socket, since these ones have power over ethernet) so that I can check it’s transmitting to the system and install the latest version of our software onto it. Then the gateway is ready to go!

Screen Shot 2016-09-06 at 11.40.00But a gateway by itself isn’t much use…. So I’ve also been involved in building ninety-six kittens. My job covered the first few steps in the process of turning a sheet of circuit boards into a fully-functioning kittens: extracting them from the sheet, plugging them in via the programming widget, and installing the software that enables them to transmit their temperature data to the gateways. Once this update was done, I soldered a radio antenna onto each kitten to improve its range of transmission – and then passed them on to Winston for some more advanced testing and the final stage of assembly.


Was it all engineering?

Screen Shot 2016-09-06 at 11.52.27No! Throughout my time here, I’ve also been involved in other aspects of the company. This means going to meetings, and getting stuck into other types of task. I spent some time doing market research for Hermione – starting with some fairly abstract googling, and ending up with a (colour coded!) spreadsheet of the relevant information.

As well as that I’ve been creating a demonstration account. This needed a major Kitten Hunt around the office to find all of the kittens left in random places during test runs (this went fine until I found some on the ceiling, which were slightly out of my reach). I then took my pile of found kittens and used the system to identify them. Those that were involved in testing were returned to the person in charge of the relevant project, and I “adopted” the rest. I then put the “adopted” kittens into a new project and spent some time creating views for them that will later be used for demonstrations.

This was a great opportunity for me to really get to grips with the data outputs for the kittens, and the full range of analysis that the software can do.

What’s it like?

It’s a really friendly company – everyone here seems to be happy to explain things to me and to teach me how to do whatever I need to know for my latest task. Being set a variety of jobs is great, as it means I get to learn loads of new stuff and see how lots of different aspects of the company work. There’s also a set of company mugs with the kitten face logo on, which I found slightly too exciting…. All in all, I’ve had a great time learning lots of new stuff, building things, and finding out about Purrmetrix during my time here!

<Awww, thanks Fiona. You’ve got great kitten herding skills! Also insane ideas of what makes a good biscuit


Interested in an intern role in Purrmetrix? Get in touch with us – we are always interested in hearing from people who want careers in engineering or marketing. Baking skills not mandatory.>


Heatmap of the month – improving energy efficiency

There are many new products that help energy managers save energy from HVAC – one of the big challenges is understanding how to use them to reduce energy without compromising comfort.

Heat maps this month comes from an estate in the North of England with a very active programme of energy reduction. They show what happens in the office over three weeks as they trial a novel system in their condenser units, which offers exciting energy savings.

Here’s the first week – a record of seven days before the system was engaged.

In the second week the set up was tested for maximum theoretical savings. It’s immediately obvious that the building is struggling to shed excess heat after a warm weekend and although the performance is better towards the middle of the week, a warm day on Friday shows that the set up needs to be backed off to maintain comfort.

Has it worked? There is obviously still a problem in week 3 which was traced to a faulty HVAC sensor, not the new system. By the end of the week the sensor is replaced, comfort is restored for all occupiers and the energy manager can collect the savings from the new system knowing the output is what it should be.

Have you got an energy efficiency initiative that needs benchmarking? Get in touch and we can help you put some hard numbers around the performance of your systems.