Another trickle vent question

[yuumei]

Sorry for what seems like a common question but I can't see the answer. I would like to install MVHR to reduce the CO2 levels in the house and eventually replace the windows to remove the trickle vent holes. However upon reading the building regulations (part F) It says:

 

"Replacing windows
Existing windows with background ventilators
3.14 If the existing windows have background ventilators, the replacement windows should include background ventilators. The new background ventilators should comply with both of the following conditions.
a. Not be smaller than the background ventilators in the original window.
b. Be controllable either automatically or by the occupant.
If the size of the background ventilators in the existing window is not known, the ventilator sizes in paragraph 3.15 may be applied."

 

Which I read as, when replacing windows if the existing ones have trickle vents, the replacements must have them too. Regardless of having MHVR or not.

 

Are only new builds allowed to get rid of trickle vents?

[JohnMo]

Read the section about ventilation. With MVHR you do not have background ventilation with MVHR, you have mechanical ventilation, so rules are different.

 

Unless your really determined to have MVHR, it is not the be all, end all solution. Trickle vents - humidity controlled (CO2 levels are closely related to humidity levels) and humidity controlled MEV (extract only in wetrooms only when required) or dMEV, can be easier to install, low running cost solution, that cost effective in use and certainly to install.

[Temp]

I swear by mvhr, best thing we included. I think the constant ventilation helps a lot with air quality. The extract might even be reducing dust levels in the house? 

 

I think having trickle vents in windows makes that area colder and more prone to condensation on glass and frames. With MVHR introducing warner air elsewhere into the room the window area is warmer and less prone to condensation. We don't get condensation on the few metal framed windows we have.

 

We dry laundry on racks in our bathroom and don't get condensation in there either. It doesn't even have an extractior fan - it relies on the mvhr extract which seems sufficient. 

 

Our set up is probably quite inefficient as we have wood burners that aren't room sealed. They only get used at Christmas so most of the time represent a big hole in the ceiling.

 

All mvhr have some sort of filter on the input and it surprised me how quick they block up. That increases the power drawn. First time ours blocked it popped the 1A fuse on the mvhr fan ! So make sure you have easy access to the filters and plan on clean them every 3-4 months. Our filters are like a coarse aquarium foam and rinse out under a tap. They get blocked with dust, flys and moths etc.

[JohnMo]

5 minutes ago, Temp said:

think having trickle vents in windows makes that area colder and more prone to condensation on glass

Hence saying use humidity activated, not manual ones, which are almost always closed at some point and never get reopened, or vise versa.

 

dMEV ventilation in summer house, currently -2, last night -5, external humidity is 87%, internal humidity is currently 32% and last night dipped down to 30%, so not sure at that level condensation would form.

 

Our house has MVHR and sits at 36%.

 

Important bit is having ventilation that does what it's supposed to do.

 

[yuumei]

Thanks both, I found a sentence:

 

"Background ventilators
1.72 To avoid unintended air pathways, background ventilators should not be installed with mechanical ventilation with heat recovery."

 

So I guess this overrides the previous statement when replacing windows.

 

Reason I'm asking is I got a CO2 monitor recently and found it goes up to about 3000 ppm overnight, we did try leaving the trickle vents open but it got very cold recently.

[yuumei]

Follow up: I asked our councils building control and they said:

Quote

 

Paragraphs 3.14-3.16 solely relate to replacement windows. You are also alerting the ventilation provisions to your house by providing a MVHR system, which as you mention shouldn’t have background ventilators as well.

Approved document F isn’t the easiest of reads how ever I believe if you are replacing your windows and installing a MVHR system, which does not require the installation of trickle vents, we would not require trickle vents to be installed to the windows regardless if the existing windows did or did not have them.

 

So as assumed you are able to, it's just the document is not correct (IMO)