Damp and dehumidifiers

[stockhausen]

As an update to this sorry tale, it seems that the Meaco dehumidifier has helped but not entirely resolved the problem of damp and mould. The warmer, dry weather can't come soon enough.

I recently saw a cheap dehumidifier in Aldi which quoted effectiveness based on an ambient temperature of 30°C and 80% relative humidity! Who on Earth uses a dehumidifier in a sauna?

 

[Doobedoo]

A dehumidifier can only extract a certain amount of water depending on the specs of the dehumidifier, it’s not a magical solution to eradicate all traces of mould, but it will help prevent the conditions that allows mould to grow.

Has your niece actually cleaned and removed the mould to begin with? Bleach may not kill all traces of mould it may appear to initially but it doesn’t necessarily kill the roots. Tea tree oil is supposed to be more effective so look that up.

My Meaco in combination with ventilation during the day and a decent bathroom extraction fan has improved our house a lot. We have almost no traces of it now compared to what the previous owners have had.

Unfortunately compressor based dehumidifiers are not as efficient at lower temps than dessicant’s but the trade off is they usually consume less power.

For example mine has written on the side of the box the following.

• 10c and 80%rh 3.20 litres per day. 115watts
• 20c and 80%rh. 7.40 litres per day. 145watts
• 30c and 80%rh. 11.50 litres per day 185watts
• 10c and 60%rh. 1.40 litres per day. 104watts
• 20c and 60%rh. 4.30 litres per day. 138watts
• 30c and 60%rh. 7.30 litres per day. 169watts

 

[stockhausen]

Any idea whether one could use PIV (Positive Input Ventilation - LINK) to bring in air via the fan-light above a front door rather than from the loft space?

I realise that the loft space is effectively an area heated (and perhaps dried) via heat escaping from the house in general whereas random air from the open air may not work. In relation to that, would running an extractor fan in reverse in a bathroom work?

 

[Mark A]

5°C and 60%rh 1.4 Litres Per Day 173 Watts
10°C and 60%rh 2.50 Litres Per Day 153 Watts
15°C and 60%rh 4.80 Litres Per Day 199 Watts
20°C and 60%rh 7.60 Litres Per Day 216 Watts
25°C and 60%rh 9.60 Litres Per Day 243 Watts
30°C and 60%rh 13.20 Litres Per Day 270 Watts
5°C and 80%rh 2.40 Litres Per Day 177 Watts
10°C and 80%rh 5.10 Litres Per Day 159 Watts
15°C and 80%rh 7.92 Litres Per Day 209 Watts
20°C and 80%rh 12.80 Litres Per Day 228 Watts
25°C and 80%rh 15.84 Litres Per Day 260 Watts
30°C and 80%rh 19.70 Litres Per Day 294 Watts

This is the specs for my 20L Meaco. Sounds like if the 12L model isn't removing enough water from the air at the house temp, then a larger model might be needed. At 20c mine pulls 7.6L while Doobedoo's pulls 4.3L. That bit extra might make all the difference if the current dehumidifier has helped but not quite solved the issue.

 

[Shimmyhill]

We fitted a PIV system a couple of years ago and it’s been amazing the difference it’s made, we went from a house where every room any cold day had windows full of condensation to having a small amount only on our north facing bay windows on the coldest days - life changing improvement as the condensation really made me miserable esp in the kitchen!

Ours is fed from the loft but could have been from outside so defi an option.

 

[Mark A]

Do you just get an electrician to fit one of these PIV systems? Do you need trickle vents installing as well, to allow the positive pressure to escape? My dehumidifier has completely solved the condensation issue in my house, but these PIV systems sound like they will be cheaper in the long run.

 

[stockhausen]

. . .
Ours [PIV system] is fed from the loft but could have been from outside so defi an option.

I have tried to do some on-line research on this and most references seem specifically to refer to feeding air from the loft space - which will typically be a few degrees warmer than the open air.

. . . however, see below. . .

Do you just get an electrician to fit one of these PIV systems? Do you need trickle vents installing as well, to allow the positive pressure to escape? . . .

I am not certain that an electrician needs, by law, to fit a PIV since it will typically feed into a hall rather than a kitchen, bathroom, etc.

HOWEVER - if you are not 100% confident about messing safely with 240 Volts - USE AN ELECTRICIAN!

As to trickle vents, the clue lies in the description, "Positive Input Ventilation".

Since the idea is to push humid air out of the house, some sort of "escape" route would seem to be essential:

Positive Input Ventilation or PIV Systems work by ensuring the movement of air from inside a property to outside from a unit. The PIV unit circulates fresh filtered air into the property at a continuous rate, encouraging movement of air and reducing excess moisture which can cause condensation and damp.

Positive Input Ventilation (PIV) systems help your whole home to breath and improve the indoor air quality by gently circulating fresh, filtered clean air into your property at a continuous rate.

Our range of Positive Input Ventilation (PIV) units help to reduce moisture trapped inside your home which if left unmanaged can cause condensation problems and lead to mould growth.

 

[Shimmyhill]

We used envirovent and already had trickle vents but was told we didn’t need them as homes aren’t sealed so air will always find a way out. I looked into all the options and could have done it cheaper but in the end glad I went with them as we ended up with a two vent system - I know they have outdoor air input options as looked at them.

Honestly I thought it was a bit snake oil and did loads of research and generally got very good reports after having the system fitted, some people complained about cold air coming in being a problem but that seemed to be with the other brand (who I can’t for the life of me think of, diy fitting option) Basically we hit desperation point, black mould and condensation making me fall out of love with the house and we ran a dehumidifier daily and had a window vac to clear the windows again daily. With the unit fitted you can feel the air quality is better, no mould and generally no condensation - the kitchen that really suffered due to cooking and washing etc has not had a drop of condensation since fitting and only our north facing bay windows get a little on the coldest days! We got rid of the dehumidifier and can dry washing indoor really quickly and still get no condensation, for us it’s been a miracle solution and I really didn’t think that was possible - I hoped it would reduce the issue but didn’t dare dream it would solve it!

As some background to our place we live in a 60s built three bedroom detached bungalow, concrete floors and brick walls - we did the usual thing of insulating the cavity, loft and fitting new double glazed windows and doors, there are four fire places here and all were blocked up - we opened one up to fit a log burner hoping that would help but it didn’t, love the wood burner tho! To be fair there was a condensation issue before we sealed the place up but it defi I got worse as we ‘improved’ the insulation etc.

 

[DarrenM343]

I've used Envirovent too. They were a PITA to get out to do the work once I placed a deposit but the work was eventually done after I threated to cancel the order. Basically I was told I'd hear from them within x days to book the slot but didn't hear anything at all, not even to tell me they're busy and ask if I'd mind waiting. It was close to two months without hearing anything that I threatened to cancel after chasing them up multiple times. They also made a mistake as the extractor they originally quoted for to fit in the kitchen would have breached fire safety rules due to the vent exhausting below stairs used to access the properties above(would fry them escaping if my flat was on fire). Luckily I raised this with them and just had to switch to a different type that seals shut with heat.
Anyway, that aside, I don't live at the place but have heard nothing from the tenant or managing agent who has been checking it so I believe it's working well and checked it over myself before the tenant moved in and thought "yep, that should work". The flat is on the ground floor of an 18th century chapel(sold walls) and suffered badly from what we're fairly confident is condensation. The flat has it's own entrance and a small loft. THe PIV unit fitted is wall mounted in the hallway due to limited loft access space. The bathroom fan was replaced by one of their continuously running units that automatically ramps up in speed as humidity rises and another was fitted in the kitchen though to the outside that works in the same way. The kitchen window can't be opened (sealed shut due to fire safety) although the cooker hood extractor vented to the outside if people actually used it (probably not) so it's great this unit will ramp up automatically in speed as humidity increases.

I would recommend them but they're not cheap and customer service I felt was pretty dire which is a shame really as it's a bit of a niche market they have and could impress so much more. I think the filter needs replacing after three years in the PIV unit so will be interesting getting them out to do that. I got a nice discount but only reducing the way overpriced parts (ducting was stupidly expensive) which also lets them down as it's pretty obvious the discount is fake.

Nearly went with nuaire but you have to get someone to fit it all. The nearest company they recommended who could supply and install was 150 miles away. This is why Envirovent have the niche market sewn up - they inspect, quote, supply & fit.