HOT Summer Incoming - Can Vent Axia Sentinel work as an A/C unit?

[JoH]

Hello everyone, 

 

New to Build Hub forum and hoped someone might be able to help?!

 

I live in a new build flat (new as of 2022) with a Vent Axia and the winter months are exceptional - keeps the heat in nicely and no issues with feeling cold at all. However, come the summer months and internal temperatures are reaching 35degrees+. Sleeping is unbearable! I have invested in some great fans that are a cold air solution however I would prefer to not have them on all the time, as the air does feel slightly stale. 

 

I am clueless as to what capabilities my Vent Axia Sentinel has but I know cold air can pass through and there is a Summer Bypass function. I was not given an instructions manual when I moved in, so most of the time I am guessing when pressing the buttons. However, does anyone know if/how I can programme to have the unit act as an A/C and a rough idea of how this will impact my energy costs? 

 

Any information would be appreciated! 

 

Thanks 

Jo 

[JohnMo]

The unit you are discussing is a ventilation unit it is likely to exchange the air in the building once every 2 to 3 hrs. Aircon will do the same, many times per hour. Ventilation flow rates are just way too low to effectively cool anything.

 

MVHR doesn't cool as such.

[BotusBuild]

JoH,

What you have does not have an A/C function. Summer bypass will continue to do the air exchanges, so drawing air from outside to in, and vice versa, so as it cools down in the evenings it'll remove the heat build up from the day.

You're better off turning it off completely in heat we have at present and drawing curtains and blinds to keep the sunshine out.

 

There may be a way of introducing a cooling coil into the ducting, but that is major retrofit and may not be that effective anyway.

 

We are all having to adapt to the conditions being caused the changes to or climate. If you want air conditioning in the flat for the handful of days each year when it currently required you'll need to install a specific unit.

 

OR, hang a bag of ice in front of a standard fan

[JoH]

13 hours ago, BotusBuild said:

JoH,

What you have does not have an A/C function. Summer bypass will continue to do the air exchanges, so drawing air from outside to in, and vice versa, so as it cools down in the evenings it'll remove the heat build up from the day.

You're better off turning it off completely in heat we have at present and drawing curtains and blinds to keep the sunshine out.

 

There may be a way of introducing a cooling coil into the ducting, but that is major retrofit and may not be that effective anyway.

 

We are all having to adapt to the conditions being caused the changes to or climate. If you want air conditioning in the flat for the handful of days each year when it currently required you'll need to install a specific unit.

 

OR, hang a bag of ice in front of a standard fan

 

Thanks for this - makes sense! Quick question on Summer Bypass function, do you suggest turning on for an hour or two during the evening to try and cool the flat down? Think you're right on the old school method of blinds to keep the sunshine out, having blackout blinds installed for that exact reason. Can't have a third summer living in the heat

[JoH]

13 hours ago, JohnMo said:

The unit you are discussing is a ventilation unit it is likely to exchange the air in the building once every 2 to 3 hrs. Aircon will do the same, many times per hour. Ventilation flow rates are just way too low to effectively cool anything.

 

MVHR doesn't cool as such.

Thanks JohnMo! Appreciate the reply. 

 

[JohnMo]

19 minutes ago, JoH said:

Think you're right on the old school method of blinds to keep the sunshine out

Our strategy is

 

Purge in morning when outside is cooler than house - open windows etc.

Blinds and windows closed until house is hotter than outside. Then if still getting solar gain, leave blinds closed, but open windows to let outside air in.

[marshian]

We have PIV unit - In the summer we run it flat out during night when air is cooler and during the morning until the unit temp sensor hits 25 deg - then it turns off until temp drops below 25

 

it’s proved very effective at cooling the house - not AC cool but just cooler than it had been before we installed it.

 

we do adopt a blinds/curtains closed on south facing side of the house which minimises solar gain during the day in the height of summer 

 

spring and autumn the solar gain is appreciated and it’s not as big as it is in summer

[Nickfromwales]

8 minutes ago, marshian said:

We have PIV unit - In the summer we run it flat out during night when air is cooler and during the morning until the unit temp sensor hits 25 deg - then it turns off until temp drops below 25

 

it’s proved very effective at cooling the house - not AC cool but just cooler than it had been before we installed it.

 

we do adopt a blinds/curtains closed on south facing side of the house which minimises solar gain during the day in the height of summer 

 

spring and autumn the solar gain is appreciated and it’s not as big as it is in summer

I’m going to look into this for this summer, as our place (stone walled colander) is utterly unbearable each summer.

Thinking to force a lot of outdoor air in to the house early evening through to early hours.

Attic ‘bedroom’ has a freestanding A/C unit which is sublime.

 

15 hours ago, JoH said:

However, come the summer months and internal temperatures are reaching 35degrees+. Sleeping is unbearable!

Yup, I hear you there. For some days my kids will crash on the settees on the ground floor, as with curtains closed and all that jazz the first floor is still near unbearable for those horribly hot days.

 

I don’t know the layout of your flat, but a decent freestanding A/C unit (large 150-180mm duct off the back which needs to be out of a window) could be placed in the kitchen and then a couple of pedestal fans could be used to blow the chilled air into the rooms off the hallway. The noise / sound from all this would then be away from the bedrooms, but would require all doors to be fully open.

 

Cooling is way more of a ballache than heating, unfortunately, and it’s clear that the developers (yet again) had no understanding of how these units would fail to perform as habitable dwellings during summer (now part O), and I guess you’re not alone there with this issue! 

[S2D2]

Find the model number of your unit then you can find the instruction manual online.

 

Summer bypass should run continually, not just a few hours a day. Some units increase fan speed to help purge heat but that's often disabled by default, sounds like it would help in your situation though. It will never be air con, just purging air which should get you closer to outdoor air temps.

 

Are you unable to open windows sufficiently? Or do you live somewhere where the outdoor air temperature is in the 30s?

[saveasteading]

How the Mediterranean deals with heat. Of course some use chillers...little ones cost about €300.

 

Build with masonry. Usually clay blocks with multiple cells. Insulation is gradually being adopted, but more for winter. Paint it white.

Tiles on the roof on a concrete structure. 

In the day this absorbs the sun, and at night cools down.

Shutters outside every sunny window, closed to keep the sun out. Opened at night.

Purge the air in tge evening.

 

Live more outdoors.

Go to bed late, after the evening air has moved through.

 

And getting used to it helps.

19 minutes ago, Nickfromwales said:

stone walled colander

 

The stone will absorb the heat. Where is the heat coming from?

[Nickfromwales]

9 minutes ago, saveasteading said:

The stone will absorb the heat. Where is the heat coming from?

Erm…….. the big shiny thing in the sky I think. 🤔 🌞 

Decrement delay is alive and kicking here, was worse when the house was grey dash but now painted white, no major impact as this just catches early N/East morning to late morning sun, but some as this also catches very late southern sun.
 

We’re semi-detached so S/E sun doesn’t do much but South to west sunshine really hammers us at the rear (yet to be painted white) so curtains just stay shut there. 
 

Rear extension is 9” brick without cavity, so flip-flops between turning into a microwave oven in summer and a fridge in winter. Will likely look into PIV in there this summer, or I’ll finally bite the bullet and do a single outdoor A/C unit > 3x internal units; the fear is wasting time and money on failed attempts which also reduce comfort (with excess noise).

 

Cooling is a pita.

[jack]

8 hours ago, JoH said:

Thanks for this - makes sense! Quick question on Summer Bypass function, do you suggest turning on for an hour or two during the evening to try and cool the flat down?  

 

In ordinary (non-bypass) operation, MVHR tries to maintain any temperature difference between the inside and the outside. On a cold day with the heating on, it recovers most of the heat from the outgoing air. Same in summer when it's cooler inside than out. In both situations, you want summer bypass off.

 

Summer bypass is used when the outside air temperature is closer to the desirable temperature than the inside temperature. For example, if it's 23 deg outside and 28 deg inside, you want summer bypass on so that the 28 deg air is entirely replaced with the 23 deg air from outside.

 

In most MVHR units, summer bypass operates automatically based on the temperature difference between inside and outside. Assuming yours has some form of automated control, check that it's operational.

 

If you can only control it manually, I'd turn summer bypass on as soon as the outside temperature is lower than the inside temperature. In the UK, that's generally late afternoon or early evening, depending on the day and the temp in the house. You can generally leave it on all night and then turn if off when the outside temperature gets higher than the inside temperature. It's also more effective if you boost the fan speed.

[marshian]

2 hours ago, Nickfromwales said:

I’m going to look into this for this summer, as our place (stone walled colander) is utterly unbearable each summer.

Thinking to force a lot of outdoor air in to the house early evening through to early hours.

Attic ‘bedroom’ has a freestanding A/C unit which is sublime.

PIV works for us most of the heat used to hit the upstairs from a poorly insulated loft (just 70mm of insulation) with a large south facing expanse of concrete roof tiles which really soak up the heat from the sun 

 

Yesterday peak day time temp outside was 22 deg C - loft temp hit 34 deg C - PIV turns off at 25 Deg C

 

Now we have 370mm (well we will have shortly when I finish the last areas)

 

I’m already seeing lower upstairs ceiling temps so it is helping

 

My main issue is Mrs Alien refuses to have windows open at night (apparently something to do with eight legged things) Not an issue in winter house doesn’t overheat then but as a result of that “commandment” I’m slightly constrained in spring, summer and autumn 

 

In life if someone gives you lemons you have to make lemon gin  

[Nickfromwales]

1 minute ago, marshian said:

PIV works for us most of the heat used to hit the upstairs from a poorly insulated loft (just 70mm of insulation) with a large south facing expanse of concrete roof tiles which really soak up the heat from the sun 

 

Yesterday peak day time temp outside was 22 deg C - loft temp hit 34 deg C - PIV turns off at 25 Deg C

 

Now we have 370mm (well we will have shortly when I finish the last areas)

 

I’m already seeing lower upstairs ceiling temps so it is helping

 

My main issue is Mrs Alien refuses to have windows open at night (apparently something to do with eight legged things) Not an issue in winter house doesn’t overheat then but as a result of that “commandment” I’m slightly constrained in spring, summer and autumn 

 

In life if someone gives you lemons you have to make lemon gin  

Why not have a fan to purge the attic space in peak summer? I did this to the ‘attic’ room and it shifted a LOT of unwanted heat and humidity, but downstairs had to work much harder to balance this out. 
 

The attic is unbearable in summer, and terrible (too warm / clammy) in winter.  The A/C unit dumps air from the room to atmosphere to cool the heat exchanger., so is a win win as it’s still purges humid air and any u wanted heat to the clouds. 
 

I refuse to work out what this costs to have two systems at war, but with 3 stories of house it’s just time to plug in, switch off, and get you to send me some of the fine lemon gin. 
 

 

 

 

 

Then I’ll swap it for IPA. 🍺 

[saveasteading]

1 hour ago, Nickfromwales said:

curtains just stay shut there.

Inside the room, so the heat is still coming in. It will then convect up into the room unless it is tight to the dealing.

Shutters are steel and outside the window, in the reveal. They get hot and it doesn't get past.

 

 

[Nickfromwales]

Just now, saveasteading said:

Inside the room, so the heat is still coming in. It will then convect up into the room unless it is tight to the dealing.

Shutters are steel and outside the window, in the reveal. They get hot and it doesn't get past.

 

 

Yup, I know…. I’d rather spend on A/C than have the house looking like a dark prison tbh. Just my preference.

 

I may look at a 2nd hand monoblock ASHP and a large fan coil unit on the landing (that used to be the box bedroom but is now a corridor to the rear bedroom in the extension, and had the stairs to the attic in it plus all the 1st floor bedrooms lead off it.

 

As usual, I’ll do more thinking than doing. 🤯

[JohnMo]

39 minutes ago, saveasteading said:

Inside the room, so the heat is still coming in. It will then convect up into the room unless it is tight to the dealing.

We have blinds inside rooms and they do a fine job of keeping the temperature manageable. If you don't have external blinds and curtains do a good enough job. Our last house was curtains and big single glazed south facing windows - that was fine also 

 

33 minutes ago, Nickfromwales said:

may look at a 2nd hand monoblock ASHP

Some new ones (ASHP) on eBay for below £1500.

[marshian]

2 hours ago, Nickfromwales said:

Why not have a fan to purge the attic space in peak summer? I did this to the ‘attic’ room and it shifted a LOT of unwanted heat and humidity, but downstairs had to work much harder to balance this out.

 

Loft has no ridge vents - fitting them would be an PITA and involve a shed load of scaffolding - it will need a roof job at some stage so I'll do that then

 

In the meantime I'm either going to put a couple of air bricks in the top of the gable ends (4 gable ends - stupid T-shaped house) or core drill a 110mm hole the equivalent of bathroom extractor vents and then put mesh ends on them - both would help a lot of trapped heat escape and possibly improved the ventilation / humidity levels in the winter

 

2 hours ago, Nickfromwales said:

I refuse to work out what this costs to have two systems at war, but with 3 stories of house it’s just time to plug in, switch off, and get you to send me some of the fine lemon gin. 
 

Then I’ll swap it for IPA. 🍺 

 

I get you on that - Lemon Gin is way better than IPA - not quite as good as ghost ship mind

[Nickfromwales]

1 hour ago, marshian said:

 

Loft has no ridge vents - fitting them would be an PITA and involve a shed load of scaffolding - it will need a roof job at some stage so I'll do that then

 

In the meantime I'm either going to put a couple of air bricks in the top of the gable ends (4 gable ends - stupid T-shaped house) or core drill a 110mm hole the equivalent of bathroom extractor vents and then put mesh ends on them - both would help a lot of trapped heat escape and possibly improved the ventilation / humidity levels in the winter

 

 

I get you on that - Lemon Gin is way better than IPA - not quite as good as ghost ship mind

Any movement of air will help a lot, and if you can have it cross-ventilate without needing any energy (fans) and maintenance then crack on.

 

When we fitted flues without scaffold we fitted the outer rubber ring on, pushed it to outside from in the attic, pulled it back against to seal against the weather, and then cemented it in. Just needs a slightly bigger core hole to allow the seal to squish down and be pushed through, so no need to be swinging off a ladder if you can core drill from inside to out?

 

Brewdog Wingman is the current favoured poison.  

[marshian]

6 minutes ago, Nickfromwales said:

Any movement of air will help a lot, and if you can have it cross-ventilate without needing any energy (fans) and maintenance then crack on.

 

That's the intention - let natural convection or if there is a bit of a breeze it'll help

 

6 minutes ago, Nickfromwales said:

When we fitted flues without scaffold we fitted the outer rubber ring on, pushed it to outside from in the attic, pulled it back against to seal against the weather, and then cemented it in. Just needs a slightly bigger core hole to allow the seal to squish down and be pushed through, so no need to be swinging off a ladder if you can core drill from inside to out?

 

I'm slightly OCD I need to drill from outside to in because the are a red cored bricks with a light buff sand finish on two outer faces - go from inside to out and I'll have a shed load of blown faces which will really piss me off every time I look at it - I made that mistake once in the seating area and I've covered it with an outside wall clock

 

6 minutes ago, Nickfromwales said:

Brewdog Wingman is the current favoured poison.  

 

Neck oil is quite good if you like Wingman

[Nickfromwales]

After years on a core drill I never got blowouts tbh. Just have to use lots of revs and near zero forward force and let the cutter do 100% of the work.

 

The ring is a good 60mm all round, so covers everything when it is in position.  

[Nickfromwales]

15 minutes ago, marshian said:

Neck oil is quite good if you like Wingman

Yup. Been on that in most hotels on tap, but not so good from a can I found.

 

Prob not helpful to the OP, unless they like ipa. If they drink enough cold beer they’ll be able to cope I guess! 😜

[marshian]

19 minutes ago, Nickfromwales said:

After years on a core drill I never got blowouts tbh. Just have to use lots of revs and near zero forward force and let the cutter do 100% of the work.

 

The ring is a good 60mm all round, so covers everything when it is in position.  

 

The bricks I have blow faces off for shits and giggles - I'll drill a pilot hole thro from the outside then core drill for an inch or so max then revert to inside the loft follow the pilot hole and do the rest from inside

 

Two of the gable ends have Fink trusses so they are fine I can centre the vent in the gable end just below the top of the trusses and have no worries about it looking odd outside

 

The other two gable end trusses one is "King Post" and the other "Queen Post" trusses so right in the centre of the gable end I have an upright so I'll have to drill off centre to the centre (if you get what I mean) and that will mess with my head

 

So I may have to put two vents in those - one on each side of the Post!!!!

 

It's OK I know I have an OCD problem - I just have to manage it

[SteamyTea]

21 hours ago, JoH said:

internal temperatures are reaching 35degrees+

WTF, that is not a ventilation problem, it is a building design problem.

I am pretty sure building built in 2022 should have been designed to combat extreme temperatures.  Are your neighbours having trouble as well?

[Nickfromwales]

50 minutes ago, marshian said:

 

The bricks I have blow faces off for shits and giggles - I'll drill a pilot hole thro from the outside then core drill for an inch or so max then revert to inside the loft follow the pilot hole and do the rest from inside

 

Two of the gable ends have Fink trusses so they are fine I can centre the vent in the gable end just below the top of the trusses and have no worries about it looking odd outside

 

The other two gable end trusses one is "King Post" and the other "Queen Post" trusses so right in the centre of the gable end I have an upright so I'll have to drill off centre to the centre (if you get what I mean) and that will mess with my head

 

So I may have to put two vents in those - one on each side of the Post!!!!

 

It's OK I know I have an OCD problem - I just have to manage it

I Fink that’ll work. 
 

Or get on the roof and dodge the core drill with vent tiles / slates?