How do you keep humidity under 70% in the UK?

Rosa_Damascena

digannio said:

A vote here for a PIV system. I moved from a house that had condensation on the windows as a virtally permanent feature to a large bungalow with a Nuaire PIV. The bungalow is virtually condensation free, there is less dust gathering, the air is fresh and cooking smells disperse quickly. It really does work. It's a bit cool (although you can adjust this on my model) just below the ceiling input unit but nothing untoward and it is pretty quiet. If we moved again I would defo have one fitted and I was fairly sceptical about the system to start with.

That alone gets my vote!!

ProTofik

OP here.

My windows yesterday at 8am, inside temperature in the morning around 17C and RH of 76%, outside 5C:



Then at around 7pm I finished installing PIV in my hallway: 



Today 8am, outside temperature again 5C, inside around 17C with RH 67%: 



I know these things take weeks to fully manifest themselves but after just around 13h of running I can already see positive results so I am very happy. Installation was relatively simple and the unit consumes just 11W per hour of running. The only downside is that the hall is a bit cooler, but I am not too worried as next month I am getting heating converted from oil to gas and I will finally have a proper learning thermostat so I'm sure it will compensate for it. 

I am running home automation and keep track of temperature and humidity. I will wait a week or two and come back here again with a graph showing how humidity levels continue to change.

Mistral001

I know that those who have installed a PIV unit think they are the best thing since sliced bread and will not be convinced otherwise, but aren't they not just another method of ventilating a house?  The air from outside is blown via the roofspace into a hallway at high level.  That air might be at 95% humidity during wet weather and if it is mild weather it will remain at pretty much 95% humitity when it enters the hallway.  So there is an argument that they do not reduce humidity any more than non mechanical means such as trickle ventilators on windows, old-fashioned wall vents or open fires. If you have no other means of ventilating rooms, then I am all for mechanically introducing air by using say a PIV unit, but if you already have ventilation then these active systems might not be needed in the first place.

ProTofik

Mistral001 said:

I know that those who have installed a PIV unit think they are the best thing since sliced bread and will not be convinced otherwise, but aren't they not just a method of ventilating a house?  The air from outside is blown via the roofspace into a hallway at high level.  That air might be at 95% humidity during wet weather and if it is mild weather it will remain at pretty much 95% humitity when it enters the hallway.  So there is an argument that they do not reduce humidity any more than non mechanical means such as trickle ventilators on windows, old-fashioned wall vents or open fires. If you have no other means of ventilating rooms, then I am all for mechanically introducing air by using say a PIV unit, but if you already have ventilation then these active systems might not be needed in the first place.

I don't have any other way other than opening windows few times a day. I don't have trickle vents, wall vents, and I decommissioned my fireplace. All my windows are sealed double glazed. I don't have cavity walls filled in yet but will do it next year.

In my old house I had full house MHRV system and I have never experienced humidity higher than 60%, whereas normally it was at around 40-50% all the time no matter the weather outside. 

Also keep in mind that 100% humidity outside does not mean 100% humidity inside. If it is 100% humidity outside at 5C, that air after being blown into the house and heated up to 20C becomes just 39%. 

At this very moment my loft is 12C and has humidity of 92%. My house right now (with PIV running) is 60% at 19C which is precisely what I would expect when heating up that air to room temperature. 

Of course, it it will happen to be 20C and 100% humidity I suspect it might increase indoor humidity but I will see when I get there. I can always write a script that will turn PIV off if humidity outside is higher than inside after doing the conversion. 

Edit: I might be wrong, but isn't it actually a law right now that every new house must be build with some sort of mechanical ventilation system? 

Mistral001

ProTofik said:

Mistral001 said:

I know that those who have installed a PIV unit think they are the best thing since sliced bread and will not be convinced otherwise, but aren't they not just a method of ventilating a house?  The air from outside is blown via the roofspace into a hallway at high level.  That air might be at 95% humidity during wet weather and if it is mild weather it will remain at pretty much 95% humitity when it enters the hallway.  So there is an argument that they do not reduce humidity any more than non mechanical means such as trickle ventilators on windows, old-fashioned wall vents or open fires. If you have no other means of ventilating rooms, then I am all for mechanically introducing air by using say a PIV unit, but if you already have ventilation then these active systems might not be needed in the first place.

I don't have any other way other than opening windows few times a day. I don't have trickle vents, wall vents, and I decommissioned my fireplace. All my windows are sealed double glazed. I don't have cavity walls filled in yet but will do it next year.

In my old house I had full house MHRV system and I have never experienced humidity higher than 60%, whereas normally it was at around 40-50% all the time no matter the weather outside. 

Also keep in mind that 100% humidity outside does not mean 100% humidity inside. If it is 100% humidity outside at 5C, that air after being blown into the house and heated up to 20C becomes just 39%. 

At this very moment my loft is 12C and has humidity of 92%. My house right now (with PIV running) is 60% at 19C which is precisely what I would expect when heating up that air to room temperature. 

Of course, it it will happen to be 20C and 100% humidity I suspect it might increase indoor humidity but I will see when I get there. I can always write a script that will turn PIV off if humidity outside is higher than inside after doing the conversion. 

Edit: I might be wrong, but isn't it actually a law right now that every new house must be build with some sort of mechanical ventilation system? 

I take your point.  The PIV system will probably work in your situation.  I have wall vents and fireplaces in my house.  I use a dehumidifier in rooms where there are no vents or fireplaces. 

I actually use a form of PIV in my house on occasions.  In true moneysaving tradition I have a home made one comprising an old fan heater whose heating element fused years ago and a board with a slot in it which fits over the roof space trap door opening.  The fan heater snugly into the slot in the board and  during sunny spells in winter the fan part of the heater can blow warmish air heated by the sunny into the roof space into the rest of the house.  Probably a form of low-grade solar heating!   

VT41

Can PIV's be installed on a flat on a first floor in a Victorian conversion? Reason why I ask is most i've read state it needs to be in the loft. 

ProTofik

VT41 said:

Can PIV's be installed on a flat on a first floor in a Victorian conversion? Reason why I ask is most i've read state it needs to be in the loft. 

AFAIK yes, just google "wall mounted PIV". 

ChasingtheWelshdream

OP, this idea has piqued my interest. 

Can I ask ( I may have missed it) if yiur house is older, or a newer house?

We do have various vents where appropriate but are finding morning condensation on the windows, even with the windows cracked open. I’m wondering if adding PIV would help, or if it aimed at newer air tight houses?

Mistral001

ChasingtheWelshdream said:

OP, this idea has piqued my interest. 

Can I ask ( I may have missed it) if yiur house is older, or a newer house?

We do have various vents where appropriate but are finding morning condensation on the windows, even with the windows cracked open. I’m wondering if adding PIV would help, or if it aimed at newer air tight houses?

As far as I am aware, the PIV units have been popularised by a Building Control regulation which came into force a few years ago  which required trickle ventilation to be provided in new homes.  PIV in most circumstances can be used instead of trickle ventilation as a way of meeting the Building Regulations. 

 They they can be used in older properties with vents but they might provide more ventilation than you really need.

coffeehound

ChasingtheWelshdream said:

. . . finding morning condensation on the windows, even with the windows cracked open.

Perhaps somewhat counterintuitive, but having windows open can create condensation on the window since it cools the indoor side of the glass, which makes it then attract condensation