VENT AXIA MVHR, replacement or cooling ideas

[neccar]

Hello guys,

 

I live in London in a high rise building, there are more than 400 flats in the building and most of us suffering from overheating during heatwaves, we have big windows and getting lots of solar gains.

My flat is a 1 bedroom flat, 43 sqm2, Flats have vent axia mvhr system installed in the void, which gives clean air to the flat, but it doesn't have summer bypass mode so during summer if outside temperature is lower than inside, this unit still recovers the heat still and inside I can see 30+ celsius temperature easily during sunny days.

Because there is no balcony, it is not possible to install a normal AC, some guys in the building installed water cooled AC systems with an internal condenser but it is very costly to install such a system, and you would use only a few weeks in a year.

I was wondering, is there any MVHR unit which can replace our vent axia and give some cooling as well? or is there any other way you would suggest us to do?

 

Regards

Edited September 6, 2018 by neccar

[le-cerveau]

My first comment would be flexible ducting (put in by builders) will cause massive flow losses.

 

Looks like a Ventaxia Integra model, small 400mm x 400mm, that will be the issue getting a unit to fit in the space.  The small Brink Sky150 is over twice a long!

 

I suspect the developer put in the cheapest/nastiest unit they could find to say they had fitted MVHR!

 

[Declan52]

Would using a reflective film on the windows to reduce solar gain not be a good first step. 

[Nickfromwales]

Hi and welcome.

You'd be into a heat pump of some type TBH, but I wonder if you'd be better off using a free standing domestic air conditioner and fitting the hot air exhaust to the flexible duct that goes to atmosphere ( so you can get rid of the nuisance heat created by cooling ). Those ducts could be disconnected, extended and fitted to a free standing unit with ease.

To clarify, I'm not suggesting fitting the cooled air outlet of the air con unit to the room ducts, just the hot air exhaust, and then simply leave the air con unit cool centrally. Open the windows just a crack and allow trickle airflow outward as that should promote a bit of airflow through the dwelling. 

[neccar]

Thanks guys for the answers, 

@le-cerveau Yes it is integra model, but it is 55x55, and 30 deep, 10 cm for the hose extensions as well so it is 75 length, but the void is big, there is space to fit sth if the deep is 30

the building is a well-known building and developer installed a comfort cooling system only 36+ floor above flats

 

@Declan52 windows already have reflective film from outside I belive, well maybe not a film but it has sth because when you look at the windows from outside you cant see inside unless there is light inside and its night, during the day you can not see inside from outside so I suspect it has some reflective structure already but not sure, also I am on 25th floor and there is no balcony, I can not install anything from outside, is there any reflective film which I can install from inside?

 

@Nickfromwales thanks Nick, I have a portable AC, i use that during hetwaves and my vent doors inside the flat can not be opened much but I put it through the vent doors as in the picture attached, but the problem is portable AC is so noisy, you can't sleep while it is running, well at least I cannot  

Edited September 6, 2018 by neccar

[dogman]

A quick option for you would be to disconnect one of the two fans in the unit as a simple summer bypass. I am assuming you have opening windows. Disconnect the intake fan in order to ensure that stale air is extracted. Keep a window open in each room to allow the cooler evening air to be pulled into the room.

Some smaller units that advertise a summer bypass use this method rather than a true bypass so check if you do replace the unit

[Nickfromwales]

46 minutes ago, neccar said:

but the problem is portable AC is so noisy, you can't sleep while it is running, well at least I cannot  

Instant solution and within budget

Bingo.

[neccar]

well, I am still hoping there might be a better solution than running a portable ac and putting ear defenders :)) 

Edited September 7, 2018 by neccar

[neccar]

19 hours ago, dogman said:

A quick option for you would be to disconnect one of the two fans in the unit as a simple summer bypass. I am assuming you have opening windows. Disconnect the intake fan in order to ensure that stale air is extracted. Keep a window open in each room to allow the cooler evening air to be pulled into the room.

 Some smaller units that advertise a summer bypass use this method rather than a true bypass so check if you do replace the unit

Thanks dogman I will try this as well, but I am still not sure even summer bypass mode will be enough to keep the flat cool or not

[dogman]

I have experience of both systems and can say that it makes a  difference having a summer bypass although not a massive difference.  What i found was that our system without a summer bypass in our rental cottage appears to make the house very hot and not able to cool down over night where our new house with a proper summer bypass, although it got hot on the worst nights this year was no where near as bad.

 

[jack]

MVHR is designed to maintain whatever temperature difference exists between inside and outside. This is generally good, except when it's too hot inside and there's cooler air available outside (ie, overnight during warm periods, or possibly even during the day depending on how hot it gets inside).

 

The problem with bypassing the heat exchanger permanently during summer is that when it's hot outside and cool inside (eg, mid-late morning on a warm day), you'll effectively be pumping out the cool air and replacing it with warm. That makes the place heat up even faster.

 

I think the simplest solution to your problem is to open the windows as wide as you can tolerate in the evening, as soon as the temperature outside drops below the interior temperature. A large, high capacity pedestal fan set up high to blow hot air out an open window will make a massive difference to bedroom temperatures before you go to bed. I find that just leaving our windows open for two or three hours before we go to bed makes a reasonable difference, but a fan will definitely improve things if you don't have good cross-ventilation or it's a still night (quite common when the weather is hot).   

 

You can turn the fan off when you go to bed and leave the window open if you find you can sleep like that. Otherwise, close the window and turn the fan to point at or near your bed on a low setting. Fans are a lot quieter than air conditioners. I lived in Australia for a while and got through 30+ degree nights with just a pedestal fan at the foot of the bed and no air conditioning.

[newhome]

I use a fan pretty effectively when it’s too hot in the house. Yes they are only effective at cooling the person next to the fan as opposed to cooling down the entire room but given that it’s personal comfort that is most important I would have thought they work as a tool to mitigate rather than address the issue. I have one downstairs next to where I sit and another in the bedroom. The quieter one is used in the bedroom. I’m the world’s worst sleeper but can sleep with it running. 

 

I might try your ‘blowing hot air out of the window’ idea @jack but not today. Today it is cold and I’m thinking of switching the heating on. Summer is over ?.