House Cooling ideas

[lizzie]

Ive held back on changing to the enthalpy exchanger and am experimenting with how I use mvhr on the advice of my installer.  Its £850 plus install for the enthalpy change now...installer thinks I dont need it.

 

I have my by pass set to manual open so it is permanently open. I am getting higher temps inside than out at certain times of the day due to the solar gain issue. I am running quite a bit of the time on the boost setting to get more cool air in.  Running on boost reduces humidity of course but with all windows open its not much of an issue. House is at about 38% humidity which is a bit low but then humidity outside is low anyway.

 

I have not been using my tumble drier in this weather other than for short bursts to finish towels. Due to dusty external conditions all other laundry is drying inside in the utility room on a folding airer.  Its not increasing humidity in the house because there is an extract vent in there. Laundry dries very quickly, its not like a conventional house at all and you dont have to worry about damp from wet washing as you might usually.

[Dreadnaught]

Some thoughts on enthalpy heat exchangers:

1. Inside humidity typically only really becomes a problem in the heights of summer or the depths of winter
2. In the depths of winter, the cold conditions lead to very low amounts of water in the outside air
3. I have heard of people rejecting the entire Passive-House concept because of low inside humidity in the depths of winter, causing nose-bleeds with family members, etc.
4. This is often caused by too much air flow and nothing to do per se with not having an enthalpy heat exchanger. Once air-flow rates are adjusted the problem usually goes away
5. For sensible heat, efficiencies of heat recovery can be as high as 95% for good normal models. For an enthalpy heat exchanger, the efficiency of sensible heat exchange is reduced, often to around 84%
6. For an enthalpy heat exchanger, the efficiency of latent heat recovery is only about 65% in the best cases as far as I have seen, not higher
7. For an enthalpy heat exchanger, the combined efficiency figures often exceed 100%. That is, it reduces the consequent evaporative cooling indoors required to re-atain an equilibrium level of humidity
8. An enthalpy heat exchanger will reduce fluctuations in the inside humidity level in relation to that outside, nothing more
9. But, based on what I have said, this increased stability will only lead to more perceived comfort at the extremes
10. And its not a magic bullet. Internal humidity will still be a complex product of the changing balance of sources and sinks of moisture combined with the effects of moisture added or removed by ventilation

Given all this, I am unsure whether its worthwhile getting an enthalpy heat exchanger. 

 

As always I am concerned foremost with comfort, not energy. And the cost does not matter either. Will I notice a difference with having an enthalpy heat exchanger or not? Is it worth it to cater for the occasional day in mid winter or mid summer? I don't know. The geek inside me wants one; the realist resists.

 

Views?

 

Edited July 12, 2018 by Dreadnaught

[SteamyTea]

2 minutes ago, Dreadnaught said:

Views?

Measure and log it, only cost 20 quid to get high quality data.

[Dreadnaught]

Just now, SteamyTea said:

Measure and log it

 

Don't have a house yet. My house is on the drawing board. Need to decide what to buy for it.

 

1 minute ago, SteamyTea said:

only cost 20 quid to get high quality data

 

Oh? What does £20 buy?

[SteamyTea]

1 minute ago, Dreadnaught said:

Oh? What does £20 buy?

Yes, Raspberry Pi Zero with wireless, a DHT22 sensor, a MicroSD card, a cheap 5V phone charger and a 4.7K resistor.

All the software is downloadable.

Job is done.

[NSS]

7 hours ago, Onoff said:

Money no object you could perhaps retrofit the "photochromic" glass as one person has done on here already. Not sure that's the right word but they will darken at the touch of a button and are linked to light level / temperature sensors.

 

£Ks per sq. metre I believe though.

Literally just back from a week's holiday. House has been locked up tight with just the Sageglass (it's actually electrochromic) and the MVHR left running (no active cooling). Temp inside upon opening the front door was a reasonably comfortable 25C in the south-facing rooms and upstairs, and 24C on the north side. As I've said before, the glass may have been expensive but it does the job, automatically, without losing the benefit of the solar gain when we want it.

[NSS]

And I should add, that's despite having multifoil insulation ?

[lizzie]

32 minutes ago, Dreadnaught said:

Some thoughts on enthalpy heat exchangers:

1. Inside humidity typically only really becomes a problem in the heights of summer or the depths of winter
2. In the depths of winter, the cold conditions lead to very low amounts of water in the outside air
3. I have heard of people rejecting the entire Passive-House concept because of low inside humidity in the depths of winter, causing nose-bleeds with family members, etc.
4. This is often caused by too much air flow and nothing to do per se with not having an enthalpy heat exchanger. Once air-flow rates are adjusted the problem usually goes away
5. For sensible heat, efficiencies of heat recovery can be as high as 95% for good normal models. For an enthalpy heat exchanger, the efficiency of sensible heat exchange is reduced, often to around 84%
6. For an enthalpy heat exchanger, the efficiency of latent heat recovery is only about 65% in the best cases as far as I have seen, not higher
7. For an enthalpy heat exchanger, the combined efficiency figures often exceed 100%. That is, it reduces the consequent evaporative cooling indoors required to re-atain an equilibrium level of humidity
8. An enthalpy heat exchanger will reduce fluctuations in the inside humidity level in relation to that outside, nothing more
9. But, based on what I have said, this increased stability will only lead to more perceived comfort at the extremes
10. And its not a magic bullet. Internal humidity will still be a complex product of the changing balance of sources and sinks of moisture combined with the effects of moisture added or removed by ventilation

Given all this, I am unsure whether its worthwhile getting an enthalpy heat exchanger. 

 

As always I am concerned foremost with comfort, not energy. And the cost does not matter either. Will I notice a difference with having an enthalpy heat exchanger or not? Is it worth it to cater for the occasional day in mid winter or mid summer? I don't know. The geek inside me wants one; the realist resists.

 

Views?

 

My installer and man who specced system both think I dont need it. They say live in the house for a while experiment with various suggested measures  of purging etc and they think it will be fine.  Will see how I go. I had the issues with nosebleeds etc when first here, was keeping windows shut and mvhr on boost, its not such a problem now I have changed the way I use it.

[Onoff]

30 minutes ago, lizzie said:

My installer and man who specced system both think I dont need it. They say live in the house for a while experiment with various suggested measures  of purging etc and they think it will be fine.  Will see how I go. I had the issues with nosebleeds etc when first here, was keeping windows shut and mvhr on boost, its not such a problem now I have changed the way I use it.

 

Nose bleeds???

 

What, was that a pressure thing?

 

You didn't suffer from the bends if you left the house too quick then?

 

 

[Jeremy Harris]

1 hour ago, Dreadnaught said:

 

I will need to do all my drying inside the house. I'm adding one of those ceiling drying rails in my laundry room. I have limited outdoor space. I considered a MVHR linked drying cupboard and would still like one.

 

My PHPP assumes 3.5 kWh of useful energy per drying event and 57 such events per year. About 200 kWh in total of cooling per year. Not much.

 

We have one of those Victorian looking hoist up rails in the utility room and I arranged it so that the utility extract vent is directly above it.  Things dry very quickly indoors I've found.

 

On the subject of humidity, I have a display in the hall that gives lots of useful information about the house, and right now it's telling me that the RH is 46%, the temperature is 22.2 deg C, the outside air temperature is 24.6 deg C and the CO₂ concentration is 456ppm.  I find that the RH tends to stay between 40% and 50% most of the time.  It might drop right down to about 35% in prolonged very cold (sub-zero) weather and occasionally rises up to around 60% in prolonged warm wet weather.  I find that I tend to suffer from rhinitis when the humidity gets too low, and haven't yet suffered from it at all here, whereas it used to be a frequent occurrence when I was working, as the RH in my office would often get down to below 30%.

[jack]

36 minutes ago, Onoff said:

Nose bleeds???

 

What, was that a pressure thing?

 

Dry air = cracked skin inside the nose = nosebleeds.

[Ferdinand]

Hoicking this thread back out of the underworld, how are bh-ers doing in the heat?

 

My house - built to 2010 building regs plus a bit better - ran all the way up to 26C yesterday in core temperature (hall stat], which is nasty for me, and I managed to purge ventilate it down to 21.5C this morning. A bit longer and I will close most of it to keep the hot air out If any appears. linterestingly I am getting cool air intoigh the South side in te last half hour.

 

The happiest people I have talked to are a couple of tenants in the nothern half of pairs of semidetached houses .. both 1900 solid walled vintage - who say it is lovely and cool.

 

F

[Jeremy Harris]

Our old house is pretty hot - mid-20's indoors and only really getting cooled at all for the first couple of hours around now, when we can have all the doors and windows open and let in some of the outside air that's around 18 deg C.  It's block and brick, with solid concrete floors, 60mm bonded bead EPS in the walls and 250mm of rockwool in the loft.  The major problem is that it has loads of glass that isn't shaded, and although the glazing is reasonably good uPVC DG, there is a terrific amount of solar gain, so all the curtains have to remain closed to even try to keep it down to the mid-20;s.

 

The new house is fine.  It sits at around 22 to 22.5 deg C inside all the time, but over the past couple of weeks the cooling system has usually had to kick in by around 3pm, although I've noticed that the cooling usually switches off by around 5pm.  I just have the floor cooling running at the moment, as an experiment to see how much warmer the upstairs gets.  Hard to be definitive, but I'd say upstairs may be around half to 1 deg warmer than downstairs.

 

I've just bought a duct cooling element, a water one, and as I was planning to relocate the MVHR intake to a lower position and position it next to the back door, but still at the rear of the house, with an added "bug filter" that can be more easily cleaned than the internal filter, I've decided to fit the duct cooler into the filter box I was making.  I'll fit a motorised valve to it and connect it directly to the ASHP, which is just a metre or so away, so that the duct cooler is only turned on when the ASHP is in cooling mode (easy to do as there are programmable relays in the ASHP, so I can programme one to come on when the ASHP is in cooling mode). 

 

A few rough sums show that this should cool the MVHR intake air down to around 13 to 14 deg C, and as the MVHR will be on full bypass in this how weather, that means that it will be blowing cool air around the house whenever the cooling system is running.  At the trickle ventilation rate the MVHR changes all the air in the house in a bit over two hours, so with the long decrement delay of the house and the effect of the slab cooling, I reckon the slight temperature increase we're seeing by mid-afternoon should be levelled out.  I may drop the cooling thermostat threshold by half a degree; it's currently set to come on at 22.5 deg C.  If it comes on at 22 deg C then I think the house would probably level out at between 21.5 and 22 deg C in hot weather like this.

 

One other point, the heat reflective film on the glazing is extremely effective.  Yesterday afternoon I was helping the fencing chap and coming in and out of the front door.  The outer door hand was almost too hot to touch, but the glass inside the house was barely warmer than the air temperature inside.

[jack]

1 hour ago, JSHarris said:

The new house is fine.  It sits at around 22 to 22.5 deg C inside all the time, but over the past couple of weeks the cooling system has usually had to kick in by around 3pm, although I've noticed that the cooling usually switches off by around 5pm.  I just have the floor cooling running at the moment, as an experiment to see how much warmer the upstairs gets.  Hard to be definitive, but I'd say upstairs may be around half to 1 deg warmer than downstairs.

 

Interesting experiment.

 

My one-wire unit is on the blink so I can't measure temperature at the moment, but I'd estimate there was at least a 5 degree difference between the upstairs and downstairs temperature when I went upstairs last night. It was a very peculiar feeling walking upstairs into a layer of air with a completely different temperature!

 

I had windows open to allow flow-through ventilation from the time I went to bed, and by this morning the temperature difference is more like 2-3 degrees. 

[Jeremy Harris]

I think that, in our case, it's because we only have two windows upstairs, one in each bedroom, and they point East and West, with the East facing one having heat reflective film on, which pretty much kills any solar gain upstairs from early morning through to mid-afternoon. 

 

 

[jack]

Certainly some of the gain upstairs is from east facing windows that only have temporary internal blockout curtains - you can feel the effect once the sun hits them in the morning.

 

I do think that the cooler downstairs is having an effect on upstairs. It's definitely cooler upstairs than it has been in similar weather recently. Whether some of this is to do with some redistribution of heat via the MVHR I don't know, but I'm convinced there's a difference.

[Ferdinand]

2 hours ago, JSHarris said:

I think that, in our case, it's because we only have two windows upstairs, one in each bedroom, and they point East and West, with the East facing one having heat reflective film on, which pretty much kills any solar gain upstairs from early morning through to mid-afternoon. 

 

 

 

Do you need a portable air con to cool it down for your viewers, and to be quickly inserted into the closet?

[Jeremy Harris]

1 hour ago, Ferdinand said:

 

Do you need a portable air con to cool it down for your viewers, and to be quickly inserted into the closet?

 

I do have a portable aircon, but it makes a heck of a noise when it's running, and only really cools down a single room.  It's also very awkward to use, as you have to feed the hot air exhaust hose out of a window, which both limits where you can put it and means that warm air can flow in from the open window.

 

At the moment we tend to use it to pre-cool the bedroom, setting it up in there in the early evening, closing the bedroom door and letting it cool the room down.  We have to turn it off before going to bed, but at least we start off with a reasonably cool bedroom.

 

(taking a break from viewers - three down, three more to go today)

[MrMagic]

Scorchio! The bedrooms have A/C, hence the 'sawtooth' graphs. The downstairs rooms are reasonably stable - the kitchen is suffering from overheating tho, keeping the blinds closed down over the bi-folds helps to keep it down a bit. Living next to a busy road during the day somewhat limits the purging options, plus we're in a kind of a dip so the through air flow is hard to achieve.

 

[jack]

On 24/07/2018 at 11:54, jack said:

Certainly some of the gain upstairs is from east facing windows that only have temporary internal blockout curtains - you can feel the effect once the sun hits them in the morning.

 

I do think that the cooler downstairs is having an effect on upstairs. It's definitely cooler upstairs than it has been in similar weather recently. Whether some of this is to do with some redistribution of heat via the MVHR I don't know, but I'm convinced there's a difference.

 

Just re-reading this and it isn't clear from my last couple of posts that I put in the code to make cooling mode accessible on our ASHP last week. I may have mentioned it on another thread.

 

Having now had another few days with the UFC on during this hot weather, I'm absolutely certain it's having a significant effect on the temperature upstairs, despite all the cooling being downstairs.

I reckon downstairs has been sitting at a very comfortable 20-21 deg C for the last few days (ASHP outputting a temperature of 16 deg C during the day - I'm just manually turning it on for most of the day while the sun is up so the PV is powering it). The temperature upstairs at the end of the day has fallen from, I guess, 26-27 deg C a few days ago to maybe 22-23 deg C last night, despite how hot it's been. Doesn't sound like much, but trying to sleep in 22 deg C compared to 26 deg C is a very different experience.

 

In any event, I'm sold on underfloor cooling as a solution for at least knocking the edges off extreme overheating once all the passive design features have been optimised. I think that if we just get external blinds installed on our bedroom windows and install the remote blind we have sitting in the garage for our rooflight, we'll have the problem completely licked for next year.

 

[lizzie]

This is my house at 6.15 this evening......outdoor has dropped from 35 earlier.  Hard to get indoor down below 25 at night.  Widows open dont think I will see much improvement until I get some shading those big west facing windows.

[jack]

Ouch, that must be horrible.  You have my sympathy.

 

You've just reminded me that I can access temperature readings on the MVHR. I'm presently showing 23.4 house temperature, and 27.9 outside (we peaked at 31 or 32 today, depending which forecast you look at).

 

Oh, and the clock in my son's room upstairs has a thermometer built in, and it's saying 24.1.

 

All a bit odd, as it's definitely much cooler down here than up there, so I'd expect the house extract temp - which should roughly be an average of upstairs and downstairs - to be lower than 23.4 deg C. Perhaps the temp on the clock is off a bit.

 

I may have to make time this weekend to see if I can get my one-wire reader up and running again, so I can start logging.

[Hecateh]

1 hour ago, lizzie said:

This is my house at 6.15 this evening......outdoor has dropped from 35 earlier.  Hard to get indoor down below 25 at night.  Widows open dont think I will see much improvement until I get some shading those big west facing windows.

 

Ow - I would be living in the shower - Today is the first day I've been uncomfortable - it's 27 degrees, I have a fan on - I know it doesn't make it any cooler but it feels cooler in the moving air.  Plus I have a flannel in a bowl of water and I keep wiping my face neck and arms; letting the fan dry them.  

 

We've just had 'our thunderstorm'  Lots of rumbling and about 10 seconds of big splatty rain.

 

My lounge faces south and my new one does too but I don't find it get's too hot in here generally - unless it's humid as now.  My bedroom is on the north so generally not to bad but tonight may be the exception.  I've been sleeping with just a sheet and the fan on since the 'summer' started

[PeterW]

Just had about 20 minutes or near biblical rain ..!! It’s now like the tropics and 95% humidity .....  

[Hecateh]

17 minutes ago, PeterW said:

Just had about 20 minutes or near biblical rain ..!! It’s now like the tropics and 95% humidity .....  

Do we need to change your name to Noah?