New member

[irnbru]

Hello everyone! Thank you for letting me join this fantastic community! I am currently doing a university project related to passive house. I am responsible for ventilation part. Cheers!

[markc]

Hi and welcome

[SteamyTea]

Welcome.

 

Ventilation is very misunderstood on here, any input would be useful.

[Seren161]

Welcome! Your contributions would be very welcome!

[Tennentslager]

Welcome @irnbru my young son.

[Adrian Walker]

10 hours ago, irnbru said:

Hello everyone! Thank you for letting me join this fantastic community! I am currently doing a university project related to passive house. I am responsible for ventilation part. Cheers!

 

Very interesting.  By ventilation do you mean MVHR and/or Airtightness?  I have an interest in peoples wellbeing in a Passive Houses.

[MDC]

11 hours ago, irnbru said:

Hello everyone! Thank you for letting me join this fantastic community! I am currently doing a university project related to passive house. I am responsible for ventilation part. Cheers!

A breath of fresh air; always welcome... aye!

[irnbru]

2 hours ago, Adrian Walker said:

 

Very interesting.  By ventilation do you mean MVHR and/or Airtightness?  I have an interest in peoples wellbeing in a Passive Houses.

Yeah, mainly the design of MVHR system. I still know very little

[SteamyTea]

13 hours ago, irnbru said:

university project

Is this a final year project?

 

One area that would be interesting is how the overall building airtightness affects the performance of the MVHR.

There seems to be 'rules of thumb' about not worth it if your house has more than 3 ACH@50Pa.

Another area that I would like to know is, how does different mass flow rates affect the energy transfer.

 

Do you have a Passivhaus to play with at the university?

Edited November 1, 2022 by SteamyTea

[Adrian Walker]

4 minutes ago, irnbru said:

Yeah, mainly the design of MVHR system. I still know very little

 

There are many knowledgeable people on here.  Having a read of this book is a good place to start.  Remember Passive House is about a Fabric First approach.

[irnbru]

2 minutes ago, SteamyTea said:

Is this a final year project?

 

One area that would be interesting is how the overall building airtightness affects the performance of the MVHR.

There seems to be 'rules of thumb' about not worth it if your house has less more than 3 ACH@50Pa.

Another area that I would like to know is, how does different mass flow rates affect the energy transfer.

 

Do you have a Passivhaus to play with at the university?

Exactly, final year project. I don't have Passivhaus to play with...unfortunately. When you said "less more than 3ACH@50Pa", you mean less than 3 or more?

[irnbru]

1 minute ago, Adrian Walker said:

 

There are many knowledgeable people on here.  Having a read of this book is a good place to start.  Remember Passive House is about a Fabric First approach.

Thank you for your recommendation!

[SteamyTea]

3 minutes ago, irnbru said:

Exactly, final year project. I don't have Passivhaus to play with...unfortunately. When you said "less more than 3ACH@50Pa", you mean less than 3 or more?

Whoops, more than, not too leaky.

 

Shall go and edit my post.

Edited November 1, 2022 by SteamyTea

[MDC]

7 minutes ago, irnbru said:

Exactly, final year project. I don't have Passivhaus to play with...unfortunately. When you said "less more than 3ACH@50Pa", you mean less than 3 or more?

We had a house with an MVHR, with 0.8ACH@50Pa [not quite passivhaus, though the heating was 14.2 sqm/a]. We switched the MVHR off, because it sucked in the local bonfires and coal fires from the neighbours. Never switched it on again. Mind you, there were only 2 of us living in 280 square metres, so there was a big volume of air to share. The house had windows too, so we opened those now and again. 

[irnbru]

2 minutes ago, MDC said:

We had a house with an MVHR, with 0.8ACH@50Pa [not quite passivhaus, though the heating was 14.2 sqm/a]. We switched the MVHR off, because it sucked in the local bonfires and coal fires from the neighbours. Never switched it on again. Mind you, there were only 2 of us living in 280 square metres, so there was a big volume of air to share. The house had windows too, so we opened those now and again. 

Thank you for sharing! In our uni final project, it's a house with 5 people there. We are still designing the house therefore I don't know the exact size but I think it won't be more than 200 m2. It seems that MVHR is definitely worth it.

[Adrian Walker]

3 minutes ago, irnbru said:

Thank you for sharing! In our uni final project, it's a house with 5 people there. We are still designing the house therefore I don't know the exact size but I think it won't be more than 200 m2. It seems that MVHR is definitely worth it.

 

It Passive House Open day in a couple of weeks - https://www.passivhaustrust.org.uk/event_detail.php?eId=1016#Participating projects

[irnbru]

As I said before, we don't have Passive Houses in the university to play with. Are there ways of predicting the airtightness? Are there softwares? 

[Adrian Walker]

8 minutes ago, irnbru said:

As I said before, we don't have Passive Houses in the university to play with. Are there ways of predicting the airtightness? Are there softwares? 

Airtightness is designed-in and measured.  Are you aware of PHPP - https://passivehouse.com/04_phpp/04_phpp.htm ?

[irnbru]

5 minutes ago, Adrian Walker said:

Airtightness is designed-in and measured.  Are you aware of PHPP - https://passivehouse.com/04_phpp/04_phpp.htm ?

I had no idea! Thank you for sharing. I'm gonna read that. The problem is that right now we are trying to calculate the infiltration losses and we've no idea of the number of air changes per hour

Edited November 1, 2022 by irnbru

[Adrian Walker]

45 minutes ago, irnbru said:

I had no idea! Thank you for sharing. I'm gonna read that. The problem is that right now we are trying to calculate the infiltration losses and we've no idea of the number of air changes per hour

 

Very low air leakage rates are required by the Passivhaus standard and must be demonstrated for each certified building by means of a “blower door” air tightness test. The air change rate must be less than or equal to 0.6 air changes per hour, under test conditions.  This site will help you - https://passipedia.org/start

Edited November 1, 2022 by Adrian Walker

[irnbru]

29 minutes ago, Adrian Walker said:

 

Very low air leakage rates are required by the Passivhaus standard and must be demonstrated for each certified building by means of a “blower door” air tightness test. The air change rate must be less than or equal to 0.6 air changes per hour, under test conditions.  This site will help you - https://passipedia.org/start

Yeah I know it. The problem is that right now there are no ways we can show that our house has an air change rate less or equal to 0.6 changes per hour...

[SteamyTea]

13 minutes ago, irnbru said:

The problem is that right now there are no ways we can show that our house has an air change rate less or equal to 0.6 changes per hour...

You ca get an air test done on it.

Either ask/beg a company that does tests, or make your own tester with a car radiator fan, manometer and a flow meter.

[Temp]

 

35 minutes ago, irnbru said:

Yeah I know it. The problem is that right now there are no ways we can show that our house has an air change rate less or equal to 0.6 changes per hour...

 

I think MVHR systems are designed to produce a target ACH (building regs use L/S) ignoring any provided by infiltration. On a calm day for example there could be very little. The 0.6 ACH figure is for Passive House standards. Less than 3.0 is the test when trying to decide if the house is even suitable for MVHR.  I think if you are tasked with designing an MVHR system you will have to assume the house is suitable or ask if its already been tested? Was it done for a previous years project perhaps?

 

If you need real world leakage rates..

 

I think measuring the actual ACH due to leaks in varying weather conditions involves using trace gasses. Not sure which trace gasses are used but you could inject one until it reaches a certain concentration, wait a few hours, remeasure the concentration and do the sums to work out how much air has got in to cause the measured dilution.  Caution: Dont just use C02 without taking safety precautions. 

 

I believe its also possible to use humans.. You can measure the volume of a bedroom and estimate the C02 production of the people sleeping in it.  Then by measuring the actual increase in C02 concentration overnight you can estimate the ACH. Ive not done the sums myself but google found ..

 

https://protonsforbreakfast.wordpress.com/2021/06/06/estimating-rates-of-air-change-in-homes/

 

 

Edited November 1, 2022 by Temp

[ProDave]

5 minutes ago, Temp said:

I think MVHR systems are designed to produce a target ACH (building regs use L/S) ignoring any provided by infiltration. On a calm day for example there could be very little. The 0.6 ACH test figure is mainly used as a pass/fail test when trying to decide if the house is even suitable for MVHR.

I thought the 0.6ACH was the requirement to be certified as a passive house?

 

In Scotland, if your air test comes in a 3 or lower, building control insist you install MVHR.

 

Ours tested at 1.4 which initially I was disappointed with, but the tester said it was the best one he had yet tested.  That surprised me.

[Temp]

8 minutes ago, ProDave said:

I thought the 0.6ACH was the requirement to be certified as a passive house?

 

In Scotland, if your air test comes in a 3 or lower, building control insist you install MVHR.

 

Yeah sorry I think you are right. Its less than 3 for MVHR. Ill edit my post.