What are the impacts and mitigations of very high winds?

[Jim K]

I live on a hill where the wind is generally stronger and, as we see from global news, the weather is getting crazier... So I was wondering:

 

What happens to the ducting and MVHR when the house is hit by 80, 100, 120+ mph winds? Do joints pop apart or damage caused by big pressure differentials?

 

One mitigation could be a pressure release valves on the intake and exhaust ducts. A spring would keep it shut but if a sudden gust comes it would let air out of the duct to reduce pressure.

 

Had anyone heard of any issues caused by storms or even hurricanes? 

[JonDoe]

before you get to the ducting you have the MVHR system, fan, heat exchanger etc. Also, given that the building should be airthight, there shouldn't be a lot of pressure differential. The cross section of the intake duct is not that big and if the air vent cover is present I don't think this should be a big issue. I would guess that it might be a good idea to keep the vents away from were the prevailing winds blow. Last year when storm eunice hit where we live we had 55 mph wind gusts. I checked the ducting and I couldn't find any leak. This is based on my very limited experience so I might be wrong.

[ProDave]

Put inlet and exhaust vents on the same wall, and on the downwind wall for your prevailing wind.  In my case they are both on the east facing wall.

 

Make the house as air tight as you can, you are obviously intending to if fitting mvhr.

 

Then i don't think you will have a problem.

 

Practical experience says on a windy day in an air tight house you can open 1 window or 1 door and you won't feel a draught entering or leaving.

 

Not as exposed as you as not on top of a hill, but I am in a windy part of the country and no problems encountered.

[ToughButterCup]

Very interesting question @Jim K ...

You might like to consider a wind break - or series of wind breaks up-wind - say a thick bush or something more formal - (of the top of my head - not knowing the context) say a car-port or a pergola, or a baffle of some sort, so long as it doesn't limit the 'suck' and 'blow' ....

 

Photos?

 

[Jim K]

The intake and exhaust will indeed be on the same southerly wall, so they are out of prevailing wind... but I look at the news and see storms across northern Europe and think, "hmm what will be a problem for me if/when that comes here?". My garage roof is surely toast, my solar panels are a small risk, but the MVHR is an unknown.

 

Regardless of how well sealed a property is, a 100mph gust over the external vents will create a big momentary pressure drop vs inside. I guess that will be ok-ish, but there's a high chance it could also cause a significant pressure difference between the intake and exhaust because they are separated by ~2m but within 2m of the building edge, so swirling wind vortexes will surely do "stuff".

 

I'm sure it's not a major concern but I'm just about to install it so I like the idea from @ToughButterCup of some sort of a wind break. I was considering a brise soleil with solar panels on it just under these vents to shade the windows. They'd have an air gap at the back to avoid hot air interfering with the vents, so with a bit of over-engineering 😄 I may be able to bolt some extra protection there, or even raise the sun break above the vents 🤔

 

 

EDIT here's a pic... It's all a bit close together because "bungalow" but this is honestly the only place the unit can go. There's about 2m between the vents, 1m diagonally from the roof. I might move it in 5+ years if we do build a small extension on the other side of the house, but for now once installed those kitchen windows will mainly be shut.

 

I guess that brise soleil would be toast long before the MVHR in this situation 😂

Edited September 5, 2023 by Jim K
added photo

[JohnMo]

I have two MVHR units, one with the inlet/outlet facing the prevailing wind the other not. Both use a combined inlet outlet unit. We are also on a hill so get some big wind. Never noticed an issue

[Jim K]

1 minute ago, JohnMo said:

I have two MVHR units, one with the inlet/outlet facing the prevailing wind the other not. Both use a combined inlet outlet unit. We are also on a hill so get some big wind. Never noticed an issue

This is good to hear, thanks

[SteamyTea]

44 minutes ago, Jim K said:

intake and exhaust will indeed be on the same southerly wall

That is one of the windier sides.

My bathroom extractor comes out on a NE facing wall.

Never been a problem.

 

[ToughButterCup]

1 hour ago, Jim K said:

...

I may be able to bolt some extra protection there, or even raise the sun break above the vents 

...

 

Idea! above

Not too far above, not too near  , but justright said Goldilocks ...😏

Edited September 5, 2023 by ToughButterCup

[saveasteading]

2 hours ago, Jim K said:

issues caused by storms or even hurricanes? 

Only that the forces and potential damage are scary up close.

But wind through ventilation systems, no. The worst I've known has been flaps on cheap louvres breaking off.

Brises soleils and canopies ok too, but they were designed as such...ie for strong uplift and rotation.

I've seen a steel building rise and fall at the ridge by many inches in a gale, and cladding rip off its fixings.

1 hour ago, JonDoe said:

This is based on my very limited experience so I might be wrong.

Too modest. You have a strong grasp of the principles. In particular that an airtight building shouldn't have much air flowing through it.

When wind blows onto an obstruction it creates a negative pressure on the other side, so the loads can be huge, even on the lee.

 

 

If you want to prepare for gales, pay attention at corners on the roof...eaves and ridge. Metal cladding needs extra fixings. Flashings too.

Also anything on the roof such as pv panels (fix them down extra tight)  and flues (stay cables if needed).

 

[SteamyTea]

45 m/s (100 MPH) winds are not unusual down here.

While some buildings do get damaged, these are nearly always when we get a much lower speed from the North.

 

[saveasteading]

5 minutes ago, SteamyTea said:

from the North

Carefully avoiding jokes..any reason?

[SteamyTea]

6 minutes ago, saveasteading said:

Carefully avoiding jokes..any reason?

Probably lack of maintenance.

And trees falling.

When we, well, you northerners, had the Beast From The East a couple of winters back, the main reason for not having power for days was trees falling, they just were not used to a northern sense of humour.

 

Had a strong easterly this morning, and for a couple of days before.

Some of my plants have been damaged in the back garden (NE facing), front of house is fine. Actually sitting out here in the sun at the moment having a cuppa.

 

Was a couple of years back in a strong easterly wind I drive from High Wycombe to Penzance and got 83 MPG. Strong winds are not always bad.

Edited September 5, 2023 by SteamyTea