Preliminary plans have arrived

[Alex C]

2 minutes ago, Robert Clark said:

Thanks for the feedback and suggestions so far.

If we scrapped the log burner, what would be a good heat source where natural gas is not available?

 

You can pretty much heat our house by getting the kids to run around and the dog farting.

[Robert Clark]

18 minutes ago, Alex C said:

You can pretty much heat our house by getting the kids to run around and the dog farting.

 

Do you ever use any heating at all?

[Jeremy Harris]

1 hour ago, Robert Clark said:

Thanks for the feedback and suggestions so far.

If we scrapped the log burner, what would be a good heat source where natural gas is not available?

 

 

We just have UFH, with the pipes cast into the passive slab foundation, so only on the ground floor.  Our absolutely worst case heating requirement, with everything in the house turned off except the heating and MVHR, no occupants, a set room temperature of 21 deg C and an outside air temperature of -10 deg C, is 1,600 W, though.  In practice the house never really needs more than about 500 W at the most, though, as with a couple of hundred watts of incidental gain from appliances etc, another couple of hundred watts from occupants and an outside air temperature in winter that averages at around 4 to 6 deg C, the house doesn't really need much in the way of heating at all.  We run the UFH from an ASHP, but that's not cost effective, as we will never recover the capital cost of the thing from the electricity it saves (we are all-electric, no mains gas here).  If we wanted the best value heating system then that would be to fit a WIllis immersion heater inline with the UFH and pump, and just use the ground floor slab as a storage heater.  Run from E7 it would only cost slightly more to run than the ASHP, and has the advantage that the capital cost would only be a couple of hundred pounds, rather than a couple of thousand for the ASHP (that difference would buy enough electricity for a decade or so of winter heating).

 

We have no other heating, other than electric towel rails in the bathrooms that are automatically switched on and off in the morning and evening on a  time switch controlled circuit (plus they have their own switches to disable them if they aren't in use).  In theory we could heat the house using the Genvex MVHR, just as we use it for comfort cooling, but in practice neither of us like the slightly dry air that warm air heating tends to give.  This is very much a personal preference thing though, as @PeterStarck uses his Genvex MVHR as their main form of heating and they are very happy with it.

 

We had an open weekend a couple of years ago, where we we had around 60 people visit the house over two days, in groups of three or four, for an hour or so each.  One couple had just completed a passive house build and had chosen to fit a tiny wood burning stove (a room sealed one, intended for use in canal boats I believe).  I think this was one of the very lowest output units that was available, around 2 to 3 kW IIRC.  They related their experience with it, when they lit it for the first time on the previous Christmas Day, when they had family around.  Apparently the living room quickly warmed up to well over 30 deg C, and even with all the windows open it was too hot, so they evacuated the room, shut the door and left it with the windows open until the fire died down and the room cooled (which was the following day, apparently).  When they visited our house they mentioned that they were in the process of getting the flue and air supply duct blocked off and having an LCD screen fitted behind the front of the stove to display a flame effect.

 

If you want real flames and a low heat output, then a bioethanol stove or fire might be worth looking at.  They don't give out much heat, don't normally need either a flue or an air supply (so good for airtightness) but they can be a bit expensive to run, if you use it a lot.  As a feature, that's only used occasionally, I think they are probably a good compromise for those that really want to have the look of open flames in a room in a passive house.

[Jeremy Harris]

1 hour ago, Alex C said:

We are next to fields and I think they put so many chemicals on them there aren't many flies left. We just seem to have a week a year when tiny storm bugs get everywhere, oh and also the ladybird invasion before Christmas, definately no window opening then.

 

I've looked at spraying the house to try and control cluster flies, but it apparently does more harm than good.  It seems that wasps feed on cluster flies and insecticide tends to kill the wasps which then removes a natural predator and tends to make the next generation of cluster flies more prolific. 

 

If someone has a foolproof method for controlling cluster flies then I'd really like to hear about it, as I've yet to find anything that works really well at either controlling them, or just dissuading them from swarming around our house at certain times of the year.

[ProDave]

We never have problems with the cluster flies entering the house or being a nuisance. But like you they crawl into the gaps around the windows outside of the seals, and when you open a window, they all come in,,half dazed.

 

When I was on the roof a few weeks back doing the stove flue, and took a few tiles off, they were there as well, under the tiles but above the roof membrane.

[Alex C]

Our house requires pretty much double the heat of JSHarris but is also about double the volume from memory. To keep the air temp at a constant 21.5 takes very little additional heat as most of it comes from cooking, appliances, showering etc but we we do tend to have 3no. 600w towel rails come on for an hour a day through the winter. This keeps the bathrooms nice and warm, dries the towels really quickly and also adds some heat into the building. We also have UFH pipes in the slab (ground floor only) just connected to the smallest gas boiler I could find which modulates down to 3kw. We don't actually need much heat in the slab to heat the house but it is much nicer walking on a 23 degree tiled floor than walking on it at 20 degrees. A small amount of heat input a couple of times a week is enough to just keep the chill off the tiles so we can walk around bare foot comfortably even in the middle of winter. We run the UFH pipes with no added heat input during the day so that any solar gain onto the slab is moved all around the ground floor rather than just making a warm strip next to the full height glazing. A log burner would create far too much of a temperature spike in a passive house, better to have a small heat output for a longer period of time.

[Robert Clark]

3 minutes ago, Alex C said:

Our house requires pretty much double the heat of JSHarris but is also about double the volume from memory. To keep the air temp at a constant 21.5 takes very little additional heat as most of it comes from cooking, appliances, showering etc but we we do tend to have 3no. 600w towel rails come on for an hour a day through the winter. This keeps the bathrooms nice and warm, dries the towels really quickly and also adds some heat into the building. We also have UFH pipes in the slab (ground floor only) just connected to the smallest gas boiler I could find which modulates down to 3kw. We don't actually need much heat in the slab to heat the house but it is much nicer walking on a 23 degree tiled floor than walking on it at 20 degrees. A small amount of heat input a couple of times a week is enough to just keep the chill off the tiles so we can walk around bare foot comfortably even in the middle of winter. We run the UFH pipes with no added heat input during the day so that any solar gain onto the slab is moved all around the ground floor rather than just making a warm strip next to the full height glazing. A log burner would create far too much of a temperature spike in a passive house, better to have a small heat output for a longer period of time.

 

We have planned to have solar thermal panels which would connect to a thermal store. Now wondering if this would be sufficient for heating a few radiators and towel rails, with an immersion heater in the heat store for emergencies?

[Alex C]

3 minutes ago, Robert Clark said:

 

We have planned to have solar thermal panels which would connect to a thermal store. Now wondering if this would be sufficient for heating a few radiators and towel rails, with an immersion heater in the heat store for emergencies?

This wouldn't work as you won't get much out of the solar thermal in winter when you need the heat. Why use solar thermal when you could just use pv and divert excess to the thermal store. PV is far more flexible than solar thermal. I have had both in the past and would not bother with solar thermal again. What other heat source have you got going into the store? I hope you weren't just planning on using the log burner

Edited January 17, 2019 by Alex C

[newhome]

3 minutes ago, Robert Clark said:

 

We have planned to have solar thermal panels which would connect to a thermal store. Now wondering if this would be sufficient for heating a few radiators and towel rails, with an immersion heater in the heat store for emergencies?

 

I have solar thermal but as @Alex C says it’s not very useful in the winter when it is most needed. If I chose again I would have PV instead. 

[Bitpipe]

1 hour ago, JSHarris said:

If you want real flames and a low heat output, then a bioethanol stove or fire might be worth looking at.  They don't give out much heat, don't normally need either a flue or an air supply (so good for airtightness) but they can be a bit expensive to run, if you use it a lot.  As a feature, that's only used occasionally, I think they are probably a good compromise for those that really want to have the look of open flames in a room in a passive house.

 

I had planned one of these but even the smallest ones still kick out 1500W ... 

[Robert Clark]

3 minutes ago, Alex C said:

This wouldn't work as you won't get much out of the solar thermal in winter when you need the heat. Why use solar thermal when you could just use pv and divert excess to the thermal store. PV is far more flexible than solar thermal. I have had both in the past and would not bother with solar thermal again. What other heat source have you got going into the store? I hope you weren't just planning on using the log burner

 

We were planning on re using some solar thermal panels that we already own, and also installing new solar PV.

[Jeremy Harris]

12 minutes ago, Robert Clark said:

 

We have planned to have solar thermal panels which would connect to a thermal store. Now wondering if this would be sufficient for heating a few radiators and towel rails, with an immersion heater in the heat store for emergencies?

 

Very much better value to go for PV panels, as you can use the energy generated for pretty much any purpose, they cost far less to install (in terms of cost per kWp), have no maintenance requirements etc.

 

We originally fitted a thermal store, but found that the heat losses from it made the services room far too hot (over 40 deg C) and cracked an oak door, as well as making the adjacent bedroom too hot in summer.  I removed the thermal store and replaced it with an electrically heated Sunamp phase change thermal battery, that works like a combi boiler, and instantly heats hot water.  It's not perfect, and Sunamp need to refine the control system, but it's massively more efficient than the thermal store.  Today, for example, our in-roof PV array had fully charged the 9 kWh capacity Sunamp by around 11:00, and I could have used the excess PV generation for the next few hours to charge my car, if it wasn't already charged up.

[newhome]

2 minutes ago, Robert Clark said:

 

We were planning on re using some solar thermal panels that we already own, and also installing new solar PV.

 

Ah well if you’ve got them anyway ... Best for DHW in summer however. 

[Alex C]

We had solar thermal on the house I knocked down. I'm afraid i didn't even bother reusing it as it was never that great and the cost of someone taking it down and putting it back again would have bought quite a few extra solar pv panels. 

[Robert Clark]

So in simple terms the Sunamp can run off solar Pv or economy 7 to heat hot water and radiators?

[Ed Davies]

42 minutes ago, Alex C said:

We also have UFH pipes in the slab (ground floor only) just connected to the smallest gas boiler I could find which modulates down to 3kw.

 

How does the cost of that work out, considering the standing charge for gas? Or do you have a requirement for gas for cooking?

[ProDave]

7 minutes ago, Ed Davies said:

 

How does the cost of that work out, considering the standing charge for gas? Or do you have a requirement for gas for cooking?

47Kg propane bottle lasts over a year for cooking and costs about £80 (expensive up here) but that is less than the standing charge for mains gas. So I doubt mains gas just for cooking would be worth it.

[Jeremy Harris]

26 minutes ago, Robert Clark said:

So in simple terms the Sunamp can run off solar Pv or economy 7 to heat hot water and radiators?

 

It's really a DHW device, but that's all that's needed for a passive house, as heating really isn't an issue worth investing serious money in, as the requirement is so low.  The Sunamp can provide DHW at around 58 deg C from a relatively small box, that can be heated up by excess PV generation if available, or boosted by E7 for two or three hours overnight if needed.  We've been guinea pigs for the technology for around three years, and recently installed their latest model, which is simpler and has about double the heat storage capacity, but I have to add that it is still a work in progress, and the control system needs a bit of refinement.  However, Sunamp are supposedly developing a new control system that may address some of the irritating failings of the current system, and once that is available the unit should be very good indeed.

 

For heating, it's dead easy with a passive house to just fit UFH inside the ground floor insulated slab and use that as a massive storage heater.  Charging this up at night, using E7, works very well, and is now how we run ours.  We have a programmer to enable the UFH charging during the E7 period and a room stat that determines whether or not the UFH actually turns on and heats the slab.  Some days in winter the slab doesn't need any heat (it's not heated up at all for the past two nights, and may well not heat up tonight, either), other days it does, and once warmed up it slowly releases heat into the house for the next day or two.

[Alex C]

1 hour ago, Ed Davies said:

 

How does the cost of that work out, considering the standing charge for gas? Or do you have a requirement for gas for cooking?

We also use gas for heating hot water during the winter and running heated towel rails as the excess from pv rarely generates enough on winter days. Maybe it would be better to have had a heat pump and be all electric but then these do have efficiency issues with getting water up to temp for DHW. I don't have an answer whether it is ultimately cheaper or more expensive but at the time it seemed a fairly simple solution. We already had gas on site so no connection cost. I think we used under 4000kw hours of gas last year and about 5000kwh electricity. We generated 5000kwh of power with pv.

[Ed Davies]

50 minutes ago, Alex C said:

I think we used under 4000kw hours of gas last year

 

Say electricity at 16p/kWh and gas at 5p/kWh (is that out of date?) so £0 .11 * 4000 = £440. Yes, that probably covers the gas standing charge and boiler service. More flexible than E7/E10 but it's all fine tuning at that point.

[Bitpipe]

In our 400m2 ish house we're spending about £1.20 on gas and 90p on electricity (once the FIT is taken into consideration, average £1.55 / day).

 

That's four of us, wife and I work from home so we're in much of each day also.