Comfort cooling MVHR

[Alex C]

33 minutes ago, JSHarris said:

 

 

Very true, and the reason that several discussions here have focussed on external methods for preventing solar radiation from getting to the inside pane of the glazing. 

 

However, the Internorm solution uses external blinds that are fitted behind an additional, opening, glass layer on the outside of the sealed unit (or at least the "internal blind" Internorm windows we looked at did).  As such, they are outside the E coated panes, so work pretty much as well as external blinds or shutters.

Internorm offer proper external blinds and also the integrated external blinds that are behind a pane of glass. There is not a massive differnence in price although the integrated ones have a lower U value as the triple glazing pane is not as wide. I have both on differnent windows and the external ones work better as the slats are much wider and work better when only partially closed. The integrated ones work very well on our smaller bathroom windows

[Jeremy Harris]

When we were looking, Internorm were not offering the external blind option, only the blinds fitted behind the extra external pane.  I seem to remember that they could still offer a PH certified solution like this, though.  I'll dig out the quote we had from them and check, as it's around 5 years ago now.

[vivienz]

I've gone for external motorised roller blinds that are made from a tough mesh. They are fixed down tte sides with wires and roll back up into a cassette that sits above the window, powder coated to the same colour as the window frames. They claim to block about 85% - 90% of solar gain and you can see through them from the inside. These have to be looked at as first fix items due to the cable that needs to run externally and also the cladding needs to have room left for the cassette above the windows. These have come in at about £4.7k for two large 3 pane windows, including installation.

[Pete]

We had the solar coating put on our Internorm windows which is very good at reducing solar gain. They do numerous types of different coatings depending on what you want to achieve. I think the best one really reduces the light coming in the window though. I know how good they are as most of you will know the problems we have had with our Internorm installation, one of the issues was we had a glazed unit put in the wrong way round and the difference in temp between the this unit and the adjacent unit was at least 10 degrees but it could have been higher as I did not sit around and monitor it all the time!

[Ferdinand]

18 minutes ago, JSHarris said:

 

 

The Internorm windows with internal blinds we were originally going to buy had 4 panes of glass, yes.  The outer pane of glass was separately hinged, so that the blind behind it could be accessed.  I can't recall the model number now, but remember that they were unable to provide the internal blind option for any glazing that needed toughened glass, so the blind option wasn't available for our gable.

 

They weren't cheap, but then it's just cost us £2.5k to fit internal blinds to our gable glazing, plus we spent over £1k of fitting solar reflective film to the outside face of it, so having a solution that addresses both privacy and solar gain within the glazing may not be that different in terms of overall cost.

 

Good point. It emphasises homework-in-advance and designing out problems. 

 

When you are doing a new build an extra 3.5k may look relatively small compared to the £xxx,xxx you have spent overall even if being careful, but it is still two months of salary after tax at average wage. OrI had a month in Australia for about that incl. Bus Class, or more practically that is roughly what I paid full central heating or replacement double glazing including doors for the Little Brown Bungalow.

 

Ferdinand

 

 

[scottishjohn]

as far as overheating i will take my advice by looking at what they do in hot countries and what they use in  super passiv or zero energy houses .

a veranda  is what is used to solve this problem,  on the south side at least ,really hot countries all round so you can move to find the coolest bit to sit and sip your mint julep 

so  again it comes back getting it designed in before building  anything  for best solution 

even the waltons had a veranda !!

I,ve always been of the impression that the real reason for external roller shutters is to keep the bad guys out ,

 

[Jeremy Harris]

2 minutes ago, scottishjohn said:

as far as overheating i will take my advice by looking at what they do in hot countries and what they use in  super passiv or zero energy houses .

a veranda  is what is used to solve this problem,  on the south side at least ,really hot countries all round so you can move to find the coolest bit to sit and sip your mint julep 

so  again it comes back getting it designed in before building  anything  for best solution 

even the waltons had a veranda !!

I,ve always been of the impression that the real reason for external roller shutters is to keep the bad guys out ,

 

 

 

Unfortunately overhangs don't really address the issue here in the UK.  They work OK in mid-summer, when the sun is high in the sky, but we've found that we don't have an over-heating issue then, the problem is Spring and Autumn, or even mid-winter (we had a hot day a week or so ago).  The key thing is that when the sun is low, on a clear day, it penetrates deeply into the house and so tends to warm up a larger area of floor, wall etc.  This then tends to heat up the whole house.  It's made worse in mid-winter as those surfaces will already be fairly warm from the heating, so it doesn't take much for a bit of solar gain to increase the room temperature a lot.

 

As an example, right now our floor is sitting at around 23 deg C, the room temperature is a bit over 22 deg C and the floor is putting about 7 or 8 W/m² of heat into the house (around 500 W or so of heating is being delivered to maintain a bit over 22 deg C right now, but it's not very cold outside, around 2.5 deg C).  If the sun warms the floor up by 1 deg C, to 24 deg C, then the heat output from just the floor alone would increase to about 17 W/m², more than doubling the heat output into the house which will cause the temperature to increase a fair bit

[Alex C]

I'm with @JSHarris on this one. We have 2.4m high glazing to the south in our living room. In June/July the most the sun comes in to the room is 1m, so overheating is not much of an issue. In the winter the sun penetrates 5m across the room and on to the wall opposite generating far more solar gain. This is not a major drama in our house as it is very open plan and any solar gain dissipates around the house pretty quickly. It would be a problem if the south facing rooms were enclosed with nowhere for the heat to travel to.

[joe90]

Sorry guys but I can’t help but laugh, I currently am not suffering from overheating, in fact can’t get the car out because of ice on the road ?. I have been told by many that I will suffer from overheating because of our large south facing conservatory, this summer will be interesting as it will be our first with a completed house (but the ASHP is doinga great job keeping the house UP to temperature).

[scottishjohn]

1 minute ago, JSHarris said:

 

 

Unfortunately overhangs don't really address the issue here in the UK.  They work OK in mid-summer, when the sun is high in the sky, but we've found that we don't have an over-heating issue then, the problem is Spring and Autumn, or even mid-winter (we had a hot day a week or so ago).  The key thing is that when the sun is low, on a clear day, it penetrates deeply into the house and so tends to warm up a larger area of floor, wall etc.  This then tends to heat up the whole house.  It's made worse in mid-winter as those surfaces will already be fairly warm from the heating, so it doesn't take much for a bit of solar gain to increase the room temperature a lot.

 

As an example, right now our floor is sitting at around 23 deg C, the room temperature is a bit over 22 deg C and the floor is putting about 7 or 8 W/m² of heat into the house (around 500 W or so of heating is being delivered to maintain a bit over 22 deg C right now, but it's not very cold outside, around 2.5 deg C).  If the sun warms the floor up by 1 deg C, to 24 deg C, then the heat output from just the floor alone would increase to about 17 W/m², more than doubling the heat output into the house which will cause the temperature to increase a fair bit

so you are really saying you have too much glass area in house and you got to shut out the nice sunshine  ?

there is no perfect solution --but for sure in summer the solar gain will be many times what it is on the good autumn and winter days .,and veranda will cure the summer problem  

and maybe if you think the autumn  sun  is such a problem you should not have as many floor to ceiling windows.maybe bottom part should by wall  

 

you never going to get what you are trying to do without a full HVAC system  and as you do everything to stop  energy usage  then that is not going to be a solution.

 

there is no solution if you want a view out of the window that goes from floor to ceiling , having too much solar gain is the price you pay 

[Gone West]

28 minutes ago, JSHarris said:

As an example, right now our floor is sitting at around 23 deg C, the room temperature is a bit over 22 deg C and the floor is putting about 7 or 8 W/m² of heat into the house (around 500 W or so of heating is being delivered to maintain a bit over 22 deg C right now, but it's not very cold outside, around 2.5 deg C).  If the sun warms the floor up by 1 deg C, to 24 deg C, then the heat output from just the floor alone would increase to about 17 W/m², more than doubling the heat output into the house which will cause the temperature to increase a fair bit

 

That's interesting, we have only a relatively small amount of south facing glazing due to planning constraints so I designed a porch, which is outside the thermal envelope, to be an area from which to harvest solar gain. Although the floor warms up fairly quickly it also cools down fairly quickly because it has no other form of heating, although it is insulated. IIRC your slab is 100mm thick and do you assume the whole thickness of the slab is at 23C and then the surface increases to 24C where the sun is shining on it. Do you have an idea of how deeply the solar heating effect penetrates into the floor?

[Jeremy Harris]

As far as heating the room goes, then it's only the surface temperature of the slab/flooring that matters, but I've no idea how far down into the slab the heat from solar gain goes.  My best guess is that it will probably go a fair way into the slab, as concrete has a reasonably high thermal conductivity (around double the thermal conductivity of water, or around 45 to 50 times that of air).

[Ferdinand]

JUst as a 'data point' this is a approx 1m overhang over south facing full height windows that has been in place since 1970.

 

This photo was taken in October 2018 and the overhang is clearly blocking the sun at this time, which must be in the late morning period of the day as that wall with the shadow line faces East.

 

The experience here is that high sun is kept out which helps with overheating in summer, but low sun penetrates, as designed back then. Last summer there were overheating issues at the height of the summer, but the room has 2 roof lights on the back which can be opened for thru ventilation.

 

The house has a PIV fan fitted as the fabric was upgraded to be better insulated and more airtight, without imo sufficient thought to the ventilation, and the T remarked on the difference.

 

For a passivehaus or near-passive with the higher spec designed to operate more precisely, I think I would not rely just on this, and would want to know what I like and do some calcs, and design in something with significant extra capacity to manage the potential issue. That might be provision for blinds, or for later fitting of an auto pending skylight for stack ventilation. But it would need more precise consideration.

 

Ferdinand

 

Edited February 1, 2019 by Ferdinand

[Onoff]

23 minutes ago, PeterStarck said:

That's interesting, we have only a relatively small amount of south facing glazing due to planning constraints so I designed a porch, which is outside the thermal envelope, to be an area from which to harvest solar gain. Although the floor warms up fairly quickly it also cools down fairly quickly because it has no other form of heating, although it is insulated. IIRC your slab is 100mm thick and do you assume the whole thickness of the slab is at 23C and then the surface increases to 24C where the sun is shining on it. Do you have an idea of how deeply the solar heating effect penetrates into the floor?

 

When you say "harvest " d'you mean duct off the hot air in the porch?

[Gone West]

6 minutes ago, Onoff said:

 

When you say "harvest " d'you mean duct off the hot air in the porch?

No, nothing as complicated. We try to KIS, so when it's warm in the porch we open the hall door. It's been extremely effective at reducing heating requirement. We've found that solar gain is easily the most effective way of heating the house but unfortunately the weather doesn't oblige very often.

[TFnovice]

15 hours ago, JSHarris said:

We are inside an AONB and in a CA, plus we're opposite a GII listed building (inside the 100m radius) so had some pretty tough planning restrictions imposed.

 

Nice once you've got your planning in place though!

[TFnovice]

5 hours ago, le-cerveau said:

 

We have internorm windows with internal blinds on all windows, the room doesn't have to be dark to keep out the solar gain, you angle the blinds to block the sun but light still gets through, you don't black out the room just tilt the blinds.  They are very effective, so much so that you remember to drop and tilt them to keep out the excessive glare, and consequently solar gain.  You can even program them to do it automatically based on the sun!  I have not yet bothered with this.

 

I was talking about continental style shutters which are either open or closed.  They do have a mid setting which lets a tiny amount of light through but not really enough.

 

I have seen the internal Venetian blinds but I don't think Internorm are offering those any more.  They said they had a lot of problems with them.  We also have quite tall windows so when the blinds are retracted they would occupy a large amount of space at the top of the window.

 

16 hours ago, Alex C said:

We have external metal venetian blinds that disappear into the wall above the window when up so they are totally invisible. They are brilliant at stopping solar gain.  I have them so they automatically tilt to track the sun but allow maximum possible view through them.

 

External Venetian blinds which retract into the reveal would be interesting.

[Stones]

16 hours ago, TFnovice said:

 

When you say 'modelling' was this done by you or did you get someone else to do this for you?  I presume it was more than just a SAP calc.

 

 

I initially modelled our build using the heat/loss spreadsheet created by @JSHarris then added additional data - solar gain, incidental gains (basically household electricity use as most of it ends up as heat energy) and the impact of wind speed.  To model solar gain I used data from the PVGIS website which has a handy calculator that lets you work out the project performance of PV systems.  It also tells you the irradiation per square metre received by panels, so by setting the slope in the calculator to 90 degrees (i.e. vertical window) you can determine a per sq m figure for solar gain.  You can also enter different orientations for the different elevations of your house.  Once you have the per sq m figure, you can multiple against the sq m of glass (excluding frame) you have for a raw figure.  In turn that has to be multiplied against the g value of the glass.  I also factored in cleanliness of the glass. From that you can determine average daily, monthly and annual levels of solar gain.  That's helpful in determining heating requirements but you need to know what the peak amount of daily solar gain is to ascertain cooling requirements.  I found a site that provided that info and multiplied the average figure by the peak factor to get peak solar gain figures (roughly speaking the multiplication factor was around double in winter reducing to x 1.5 in summer).  The end result was I could quantify in kWh how much solar gain there would be and how much I would have to mitigate to maintain my desired indoor temperature. 

  

2 hours ago, scottishjohn said:

as far as overheating i will take my advice by looking at what they do in hot countries and what they use in  super passiv or zero energy houses .

a veranda  is what is used to solve this problem,  on the south side at least ,really hot countries all round so you can move to find the coolest bit to sit and sip your mint julep 

so  again it comes back getting it designed in before building  anything  for best solution 

even the waltons had a veranda !!

I,ve always been of the impression that the real reason for external roller shutters is to keep the bad guys out ,

 

 

Agree that designing in is the best solution, but as pointed out earlier, it really depends on the extent of the overheating issue.  The longer the overheating season for your particular site / build, the larger the overhangs have to be.  

[TFnovice]

2 hours ago, vivienz said:

I've gone for external motorised roller blinds that are made from a tough mesh. They are fixed down tte sides with wires and roll back up into a cassette that sits above the window, powder coated to the same colour as the window frames.

 

Sounds interesting - could you post a photo and details of the manufacturer?

 

2 hours ago, Pete said:

We had the solar coating put on our Internorm windows which is very good at reducing solar gain. They do numerous types of different coatings depending on what you want to achieve.

 

Also interesting - which coating type did you go for?

[TFnovice]

4 minutes ago, Stones said:

I initially modelled our build using the heat/loss spreadsheet created by @JSHarris then added additional data - solar gain, incidental gains (basically household electricity use as most of it ends up as heat energy) and the impact of wind speed.  To model solar gain I used data from the PVGIS website which has a handy calculator that lets you work out the project performance of PV systems.  It also tells you the irradiation per square metre received by panels, so by setting the slope in the calculator to 90 degrees (i.e. vertical window) you can determine a per sq m figure for solar gain.  You can also enter different orientations for the different elevations of your house.  Once you have the per sq m figure, you can multiple against the sq m of glass (excluding frame) you have for a raw figure.  In turn that has to be multiplied against the g value of the glass.  I also factored in cleanliness of the glass. From that you can determine average daily, monthly and annual levels of solar gain.  That's helpful in determining heating requirements but you need to know what the peak amount of daily solar gain is to ascertain cooling requirements.  I found a site that provided that info and multiplied the average figure by the peak factor to get peak solar gain figures (roughly speaking the multiplication factor was around double in winter reducing to x 1.5 in summer).  The end result was I could quantify in kWh how much solar gain there would be and how much I would have to mitigate to maintain my desired indoor temperature. 

 

 

Wow.  Sounds like I have some work to do!

[le-cerveau]

1 hour ago, TFnovice said:

but I don't think Internorm are offering those any more

Ours have only been in just over a year and if you check online they are still available and in the 2018/2019 catalogue.

[Pete]

2 hours ago, TFnovice said:

 

Sounds interesting - could you post a photo and details of the manufacturer?

 

 

Also interesting - which coating type did you go for?

Solar block glasss with SKN coating and IBE light, that is as much as I know.

[TFnovice]

1 hour ago, le-cerveau said:

Ours have only been in just over a year and if you check online they are still available and in the 2018/2019 catalogue.

 

Interesting - one of their agents/installers told me they were being withdrawn as they were a huge maintenance nightmare.  Maybe it was just that agent who was fed up of calls outs to fix.

[Jeremy Harris]

12 minutes ago, TFnovice said:

 

Interesting - one of their agents/installers told me they were being withdrawn as they were a huge maintenance nightmare.  Maybe it was just that agent who was fed up of calls outs to fix.

 

We were told much the same by the Internorm agent near us about 5 or 6 years ago now!

[Barney12]

31 minutes ago, TFnovice said:

 

Interesting - one of their agents/installers told me they were being withdrawn as they were a huge maintenance nightmare.  Maybe it was just that agent who was fed up of calls outs to fix.

 

I was really keen on the idea of external motorised blinds but I couldn't find a single installer/manufacturer that was prepared to supply/install on our exposed site. It seems they all have a reputation for being unreliable with the motors being the vulnerable point. Someone more technical than me can explain how ultra reliable garage door motors can be made but not this, size I guess?

 

P.S. Quite a shame really might have helped reduce the number of leaks from my Internorm windows

P.P.S. I'm waiting for the UK Technical Director of Internorm to visit my site. His diary was booked three months ahead. What does this tell you?

 

Edited February 1, 2019 by Barney12