Which trade for MEV for house overheating

[geojay]

We recently had an energy consultant visit us to get some advice on how to tackle the overheating of our 15 year old three storey house. One of the strategies he talked about was using MEV to help pull cooler air up through the house in the summer while exhausting the warm air on the top floor. We’d like to pursue this but are not sure which trade to engage with, can someone advise?

It sounds like we basically need uprated extractor fans. He tested the flow rate on our bathroom and kitchen fans and they fell far short of what they should already doing for those rooms. We’d definitely get the bathroom extractor improved on top floor and maybe have inlets in other locations on the top floor too.

FWIW, we’ve already recently fitted our Velux windows on the top floor with external blinds (we’ve had internal for years) and are getting external cassette blinds for the south facing windows on the top floor or two.

 

[MNW67]

We don't have a big problem with overheating here.

But it occasionally gets a bit hot in the summer when trying to sleep. Maybe three or four days a year. So, I have thought about it from time to time. I came to the conclusion that all the passive options probably end up costing more than getting air conditioning fitted. I would do that if I had a serious problem.

External blinds seemed very expensive last time I looked, but they should make a big difference.

 

[foxhole]

Just leave Velux open , creates a chimney effect .

 

[geojay]

Can anyone help with my question of which trade would deal with supplying and installing MEV for a house?

 

[MNW67]

Can anyone help with my question of which trade would deal with supplying and installing MEV for a house?

This is only a guess, but possibly HVAC?

Will it be one of those set ups with a heat exchanger?

 

[Harry Bloomfield]

Just leave Velux open , creates a chimney effect .

I agree. An open Velux at the top, with a door or window open at the bottom, both fitted with fly screens, are probably all you might need.

It sounds like we basically need uprated extractor fans. He tested the flow rate on our bathroom and kitchen fans and they fell far short of what they should already doing for those rooms.

Flow rate out, is very dependent on flow rate in. If the place is too well sealed, then the extract flow might well be poor.

 

[MNW67]

I agree. An open Velux at the top, with a door or window open at the bottom, both fitted with fly screens, are probably all you might need.

Most people don't want to leave a downstairs door or window open all night. There is a very small window (pardon the pun) for making this work. Many people go to bed around eleven. On a very hot day, the temperature outside probably doesn't drop below the inside temperature until about eight. In my experience, the most effective cooling is from a gentle breeze in the right direction. That provides many more room changes of air than any chimney effect. When it's really hot, and the breeze is the wrong way, which hasn't happened for a few years, I either sleep on the other side of the house or downstairs.

 

[Harry Bloomfield]

Most people don't want to leave a downstairs door or window open all night.

I agree, but it might offer a during the day solution.

In my experience, the most effective cooling is from a gentle breeze in the right direction. That provides many more room changes of air than any chimney effect. When it's really hot, and the breeze is the wrong way, which hasn't happened for a few years, I either sleep on the other side of the house or downstairs.

As already said, we open west and east facing upstairs windows, last thing at night, to try to expel the heat. Usually that works well, but not nearly as effective last night (see the graphs I posted earlier). Last year I replaced the centre light, with a fan/light unit, to avoid the need for a portable unit.

The upstairs is always warmer than down, so in hot weather, in addition to opening windows, we set the fan to run for an hour or so. Last night, there was no breeze to help ventilate the house, so we ran the fan the entire night, until we got up.

 

[MNW67]

I agree, but it might offer a during the day solution.

Maybe others houses are different. But here we only struggle on extremely hot days and on those days the temperature outside is usually several degrees warmer than inside. So bringing in outside air is counterproductive.

 

[Notch7]

Modern U.K. houses are designed mostly with thermal mass on the cold side and insulation on the warm side…..which makes them efficient to heat but difficult to cool.

Old houses have thick solid brick walls and solid floors, which can really help keep rooms cool.

 

[foxhole]

We just use a fan , or chilled fan when very hot, not noticed any real heat yet.