Does anyone with MVHR have annual internal temperature and humidity data?

[SteamyTea]

1 hour ago, Adsibob said:

I do. The only problem is that I have it individually for each room of the house and you can only see the data 24hr at a time. 

Easy enough to concatenate files with the command prompt:

 

 

[JohnMo]

Think if your design requires a tight control on internal or external humidity, I think you change design.

 

Summer humidity even with MVHR is all over the place, especially if you are cooling, have the windows open or both.

 

We were hot this morning, cooling on (always on really in summer) 59% at midnight and by 8am at 69%, house basically cooler than outside. House between 20 and 22 outside 22 to 25. Over the last month has been mid 50s and above.

[Kelvin]

Indeed. This was the change over 24 hours

 

[Mike]

On 05/08/2024 at 20:52, JohnMo said:

Summer humidity even with MVHR is all over the place, especially if you are cooling, have the windows open or both.

 

We were hot this morning, cooling on (always on really in summer) 59% at midnight and by 8am at 69%, house basically cooler than outside.

It takes moisture vapour hours to travel through the thickness of plasterboard*, so daily variations are immaterial. It's the flow over the course of weeks that's important, and that's where real-world data would be very helpful.

 

*e.g. Mortensen, L. H., Rode, C, & Peuhkuri, R. H. (2005). Full scale tests of moisture buffer capacity of wall materials. In G. Johannesson (Ed.), Proceedings ofthe 7th Symposium on Building Physics in the Nordic Countries (Voi. Volume 2, pp. 662-669). The Icelandic Building Research Institute, IBRI.  https://findit.dtu.dk/en/catalog/537f0d1c7401dbcc12009157

 

On 05/08/2024 at 18:56, SteamyTea said:

On 05/08/2024 at 17:07, Adsibob said:

I do. The only problem is that I have it individually for each room of the house and you can only see the data 24hr at a time. 

Easy enough to concatenate files with the command prompt:

I'm sure that I can manipulate data provided in any format, by the minute, day or whatever, as long I know what it all represents.

Edited August 7 by Mike

[JohnMo]

3 minutes ago, Mike said:

takes moisture vapour hours to travel through the thickness of plasterboard*, so daily variations are immaterial.

So minimum humidity monthly average (May) was 52%  then in June average starts to increases to 60%. 

[SteamyTea]

1 hour ago, Mike said:

I'm sure that I can manipulate data provided in any format, by the minute, day or whatever, as long I know what it all represents

Post up a sample.

[Adsibob]

2 hours ago, Mike said:

 

 

I'm sure that I can manipulate data provided in any format, by the minute, day or whatever, as long I know what it all represents.

I’m not sure you can if the “data” is basically an image, like this, for each room of the house and for each day of the year:

 

[Mike]

On 07/08/2024 at 19:42, Adsibob said:

I’m not sure you can if the “data” is basically an image, like this, for each room of the house and for each day of the year:

Yes, somewhat tricky if you have no access to the data...

[Sparrowhawk]

On 16/06/2024 at 23:15, Mike said:

Adding an smart vapour check, such as Intello (which lets vapour through in both directions at a variable rate depending on the temperature differential between the two sides) is likely to be a better option.

Did you / have you looked at the Siga Hygrobrid one-way membranes? Their data is hidden behind a login wall, the best link I can find is https://www.architectureanddesign.com.au/getattachment/c5861842-768b-451a-badf-fbedef41e1f3/attachment.aspx

 

Alan Budden used the Siga Marjrex single directional vapour control layer in his retrofit and said it allowed extra IWI than moisture calculations without it did. A little more data here on page 9 of this transcript at 21:10.

[Mike]

5 hours ago, Sparrowhawk said:

Did you / have you looked at the Siga Hygrobrid one-way membranes?

I'd come across it, but not studied it until today, thanks to your prompt - thanks!  I see that they're marketing the technology as Hygrobrid, but the product as Majrex, which makes it easier to find the product information:  https://www.siga.swiss/global_en/products/majrex

 

Where it's feasible to seal all penetrations against vapour ingress it it does look interesting, particularly for anyone designing a flat roof, which in theory would be ideal for me.

 

However, In my particular case I'm sure that some moisture vapour will bypass any vapour membrane via the partitions that pass through the ceiling level up to the underside of the floor sheeting above. In those circumstances although Majrex lets vapour out 3 times more quickly than when it's letting it in (g-value vapour resistance @50% RH 'out' at 25 MNs/g, and 'in' at 75 MNs/g), Intello lets vapour out twice as fast as Majrex (g-value @50% RH about 13 MNs/g). Though it lets in nearly 6 times as fast as Majrex too. I can't spot a chart for Majrex that shows g-value for other humidity levels.

 

So the question becomes which product keeps moisture levels in the insulation lowest for longest (or the opposite). I don't have an objective way to answer that, but Majrex is now a candidate, if I choose to add a membrane.

 

[marshian]

As I said earlier I've been logging for a while

 

My External Sensor (Tempo and Humidity) is actually in a well ventilated loft

 

My Internal Sensor (Temp and Humidity is in one of the bedroom)

 

Hopefully this table will work OK

 

Month	Avg External Temp	Avg External Humidity	Avg Internal Temp	Avg Internal Humidity
Aug-23	20	62%	23	60%
Sep-23	20	68%	22	64%
Oct-23	15	80%	19	67%
Nov-23	9	89%	13	73%
Dec-23	10	91%	15	69%
Jan-24	8	86%	14	64%
Feb-24	11	86%	15	67%
Mar-24	12	79%	16	66%
Apr-24	13	70%	17	63%
May-24	18	66%	20	65%
Jun-24	19	58%	21	59%
Jul-24	20	61%	23	59%
Aug-24	21	57%	24	56%
Sep-24	18	70%	21	64%

 

Interested in Mike's xls sheet I plugged this years data into it

 

 

[Mike]

Thanks @marshian - great to see some real data :)

[Mike]

39 minutes ago, marshian said:

Interested in Mike's xls sheet I plugged this years data into it

I've added the rest, plus an extra line to separate out how much additional humidity is being added internally (as opposed to due to the humidity of the external air):

 

 

And turned it into a graph:

 

Very helpful - thanks again!

 

[marshian]

5 minutes ago, Mike said:

I've added the rest, plus an extra line to separate out how much additional humidity is being added internally (as opposed to due to the humidity of the external air):

 

 

And turned it into a graph:

 

Very helpful - thanks again!

 

 

Nice work

 

I'd better add a bit more info

 

We have a PIV unit installed - takes air from the loft and pushes it into the house - it's not MVHR but it solved the issue when I insulated under the ground floor and humidity levels spiked due to the reduction in drafts.

 

It cuts off at anything above 25 deg in the loft (so summer during the daytime it's mostly off)

 

It does a fairly good job run (08:30 to 15:00 provided the loft temps don't turn it off early) and 00:00 to 06:00 overnight when we are the main drivers for humidity (Sleeping)

 

I've never calibrated the Humidity and Temp Sensors but from a temp perspective they are pretty damn close to other devices reporting temps so I'm comfortable with trusting the info

 

What I would say is that all my humidity readings I feel are on the high side and I'd like them to be lower but when we ventilate the house on good dry and sunny days the readings go a lot lower into the low 40's (much lower than the loft!!!)

 

Last thing the room with the sensor is heated in winter but on a set back temp to the rest of the house as it's north facing - has three external walls and loses a shit load of temp very easily (last winter it also had a large area off loft insulation missing) - If I'm in that room working on my PC it heats up quite quickly

[Mike]

10 minutes ago, marshian said:

We have a PIV unit installed

Yes, I  spotted that on the previous page, but it's interesting to learn more about how and when you use it, and your reasoning and experience. If it was run all the time, or faster, I'd expect that the humidity would fall a bit more, but it seems that you've got it in a fairly comfortable range, and it's good that it solved your humidity problem.

 

PIV isn't too far off from MVHR in terms of renewing the air, so the data is still very useful in helping me determine a potential internal humidity range, despite all the variables that come into play. There are a few studies published suggesting that a family of X people may generate Y litres of water over the course of Z time, but that's just not helpful in this context.

[marshian]

5 hours ago, Mike said:

Yes, I  spotted that on the previous page, but it's interesting to learn more about how and when you use it, and your reasoning and experience. If it was run all the time, or faster, I'd expect that the humidity would fall a bit more, but it seems that you've got it in a fairly comfortable range, and it's good that it solved your humidity problem.

 

PIV isn't too far off from MVHR in terms of renewing the air, so the data is still very useful in helping me determine a potential internal humidity range, despite all the variables that come into play. There are a few studies published suggesting that a family of X people may generate Y litres of water over the course of Z time, but that's just not helpful in this context.

 

On the run time - it's basically set to when we aren't home or are asleep

 

Power consumption is 9W when running so from memory I must have set it on either 3 or maybe 4 out of the 6 settings - It's been a long time since I changed the speed

 

Claimed air volume on each of the power settings is

 

Setting	Litres/sec	Litres/min	Litres/Hr	Hrs for 1 AC
1	10	600	36000	8.08
2	20	1200	72000	4.04
3	30	1800	108000	2.69
4	40	2400	144000	2.02
5	50	3000	180000	1.62
6	60	3600	216000	1.35

 

The Hrs for 1 AC (OK I know it's not going to drive all the air out there is going to be some mixing) are what I calculated based on volume of the house.