Trickle vents and retrofit

[JohnMo]

23 minutes ago, Gone West said:

Run off the battery system, charged by PVs and off peak cheap electricity.

Still doesn't make it cheap - PV generation likely to be nil, when you have your heater on. It will draw 400-500W. So will soon deplete battery with anything else on drawing load.

[Nickfromwales]

Yup, but I guess there’s some long term savings if you can afford to invest significantly in renewable solutions (boosted ROI by getting closer to 100% self consumption etc).
 

Defo a high, constant draw, as it’s resistive heating. The heater would be on pretty much 100% of time the unit is supplying input air during winter. 
 

@Gone West, do you have any kind of thermostatic or timed control over the post heater, or do you just let it ‘do its thing’?
 

I’d still bend over backwards to get MVHR installed.

[Gone West]

20 minutes ago, Nickfromwales said:

do you have any kind of thermostatic or timed control over the post heater, or do you just let it ‘do its thing’?

It's all just thoughts at the moment, although it would have a thermostat.

[JohnMo]

dMEV or MEV, humidity activated trickle vents or wall vents. Demand based running on MEV or dMEV, this would be on humidity as minimum but you could co2 if really wanted.

 

Fresh air only where and when needed. Minimal heat loss via ventilation. I posted a couple of years ago a report on a block of flats, all built a to an identical spec except for ventilation. One MVHR the demand activated MEV. Heat loss was almost the same, running cost for me way lower than MVHR, one fan no filters to change - zero maintenance.

[Gone West]

15 hours ago, JohnMo said:

humidity activated trickle vents

Surely whether humidity activated or manual, when open, they rely on the wind to work. I thought the idea that trickle vents worked correctly, had been debunked years ago.

[JohnMo]

12 minutes ago, Gone West said:

Surely whether humidity activated or manual, when open, they rely on the wind to work. I thought the idea that trickle vents worked correctly, had been debunked years ago.

Trickle vents with intermittent fan are sh!te. I am not saying to use intermittent fans I am saying MEV or dMEV. These run all the time. You will have door undercuts as well. Manual trickle vents just get shut by home owner and never opened ever again.

 

Basic process is, no one home humidity activated trickle vents (installed in dry rooms only) close to minimum settings, fan run(s) at lowest speed. All done automatically. People come home sit and watch TV or go to bedrooms, the trickle vents sense a rise in humidity after a given time, and will start to open. This allows a flow of air across the room, air will migrate to to closest fan, it will sense humidity and speed will be increased. As people move about the house this process alters, to suit which rooms or activities are ongoing.

 

Nothing wrong with a well thought out ventilation system, implemented well.

Edited October 6 by JohnMo

[Gone West]

8 hours ago, JohnMo said:

Basic process is, no one home humidity activated trickle vents (installed in dry rooms only) close to minimum settings, fan run(s) at lowest speed. All done automatically.

This is an old bungalow, so is there any reason I shouldn't have ceiling mounted humidity activated vents in the dry rooms?

[JohnMo]

1 hour ago, Gone West said:

This is an old bungalow, so is there any reason I shouldn't have ceiling mounted humidity activated vents in the dry rooms?

No reason at all, but are you just making things complicated?

[Gone West]

15 hours ago, JohnMo said:

No reason at all, but are you just making things complicated?

I have fitted several new windows already which don't have trickle vents. I don't like the look of trickle vents, and retro fitting them seems like much more of a PITA than a small hole on the ceiling.

[JohnMo]

32 minutes ago, Gone West said:

small hole on the ceiling

So what is feeding the small air? Where is the fresh air coming from?

[Gone West]

Just now, JohnMo said:

So what is feeding the small air? Where is the fresh air coming from?

The fresh air is coming from the loft, same as if I had a PIV system.

[craig]

Old cottage you say, do you have any wall vents?

[marshian]

On 04/10/2025 at 10:02, Onoff said:

Doesn't a positive ventilation unit push "heat" out through the trickle vents though thus your bills go up?

 

It can if you set it up badly ie too fast for the what is required.

 

One I have fitted has 6 speeds

 

Lowest speed is 10 l/s - Fastest speed is 60 l/s

 

My house volume is 290,700 Litres

 

This means

 

On the lowest speed it's taking 8 hours to "Theoretically" do a complete air change in the house

 

On the highest speed it's taking 1.4 hours to "Theoretically" do a complete air change in the house

 

I have humidity monitoring in several rooms in the house and basically experimented with speed settings whilst looking at the humidity data trends to determine the speed that worked best (basically speed 3 or 4 during heating season)

 

I do run the PIV unit differently in "Heating seasons" to "Non Heating seasons" 

 

Autumn, Winter and Spring - Schedule is as follows

 

00:00 to 06:30 On

06:30 to 08:30 Off

08:30 to 17:00 On

17:00 to 00:00 Off

 

Fundamentally it's on when we are asleep or not in the house

 

Summer (it's run on speed 6)

 

00:00 to 06:30 On

06:30 to 08:30 On

08:30 to 17:00 On

17:00 to 00:00 On

 

Reason for the difference in schedules is when loft temps go above 27 deg it shuts down so it's probably off for 40% of the day and in order to hit a reasonable air changes I increase the speed

 

It has an inbuilt direct electric heater but I don't use it - never found the need to use it (I accidentally used it for three days when on holiday and we had a sharp cold snap and I didn't like the kWh used)

 

As I said my house isn't Built Tight it's leaky (Not as leaky as it was but no where near the std of most builds on here) and I'd rather control the ventilation in the "out direction" than "uncontrolled in"

 

I think I covered the reason for fitting in another thread but in a nutshell I made a significant improvement to my house insulation (Suspended wooden ground floor that had a well ventilated crawl space under it) I insulated under the floors with 75mm PIR between the 100mm floor joists all 56 m2 of it

 

I already had humidity monitoring and the readings spiked as we had lost some uncontrolled ventilation from below the floor - Condensation on the inside of double glazed windows and doors on cold mornings was typical - we hadn't seen that since fitting SUDG to replace single glazed wooden windows back in mid 90's.

 

PIV fitted and all the humidity levels dropped back to same or lower than previous and only place we ever see condensation on the inside of windows is when cooking in the kitchen without either extractor fan on above the hob or opening a window slightly

 

Slightly longer reply than intended - sorry

[JohnMo]

6 minutes ago, marshian said:

Slightly longer reply than intended - sorry

But a good one👍

[marshian]

Just one more point - people and their activities are the problem with humidity levels in houses - especially when you improve the leaky nature of older houses where they were never designed to be sealed up.

 

Google says on average

 

A person exhales 400g of water a day that is released into the air

Boiling a kettle puts 10g of water on each occasion released into the air

Cooking on a hob for 10 mins can generate 100g of water released into the air

Bathing or showering can release 1.7 kgs into the air

 

Total water vapour released by a single person doing all of the above daily can be as much as 2.5 kgs of water.

 

If it isn't removed it's going to cause damp or mould 

 

The primary exit routes for PIV forced air into my house are Bathrooms (Fans are on timers but only run for 30 mins and aren't ones that close the pathway) Kitchens, Keyholes (I know it sounds mad but you can feel air coming thro them) Letterbox and 30 year old rubber seals on windows and some of the doors - all of that is enough to provide exit routes for ventilation out of the house