Have ventilation system, now need central heating system: gas vs heat pumps?

Forums › Home Workshop DIY › Have ventilation system, now need central heating system: gas vs heat pumps?

Castleisland

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#106646 28-Jul-2012 14:45

We bought a 1913 villa in Mt Eden early last year.? With severe condensation issues we installed a ventilation system (having had and enjoyed one in our previous - 1990s - house).?

Now the condensation is largely overcome, but we are still cold 2 winters later.? There is relatively new ceiling insulation (+/- 4 yrs) and we are currently getting quotes for underfloor insulation (probably going with Greenstuf, professionally installed: quoted $19.50/m incl gst and installation, comments on this also welcome).

We have a flued gas fire in the tv room, an unflued wall mounted gas heater in the central hallway (that we only use when temperature in house is below 17, for short amounts of time, but would rather not use at all), other rooms heated with portable electric heaters as needed (mainly oil column heaters in bedrooms).

Have this week been given an estimate for a central heating heat pump system (about $10K), to think about alongside the quote for a single, floor mounted heat pump for the hallway ($3500).? I'm worried that heat pumps might not work successfully with the ventilation system.?? I've now been looking at other options (thanks to all the writers re heat pumps vs gas central heating!) and am yet to work out which one will work best with the ventilation system.

Any ideas/advice re this much appreciated, as we weigh up how to best pour more money into this lovely old home (- and yes, we should have looked at this prior to putting in the ventilation system!)

{MOD EDIT : SP : Moved forum}

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#663356 28-Jul-2012 17:13

hope you have read this topic, should help you

http://www.geekzone.co.nz/forums.asp?forumid=141&topicid=106078

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RunningMan

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#663357 28-Jul-2012 17:18

We installed a ducted heat pump system several years ago. Very highly recommend the idea, if it can be installed in your house.

Ours was set up with a damper that can be opened to draw in a portion of fresh air from outside, so covers off the function of a ventilation system as well. You can also cool / dehumidify in the middle of summer which is quite nice.

Make sure the installer uses adjustable supply vents in to each room, so you can shut off the supply to unused rooms if you want (no point paying to heat unused rooms). Also consider where the return air vents go - one central one, or individual ones in each room so it works better with all the doors shut.

tardtasticx

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#663360 28-Jul-2012 17:24

We discussed this in a lecture the other day, and it was repeated over and over and over, heat pumps are the most efficient form of heating on the market today. Something like ever $1 in gets $3-4 back. So theres all this extra heat there being pushed in by this pump, imagine how much you'd have to spend on your gas heater just to get it to put the same amount into the house? More hot air from the heat pump = more hot air for your ventilation system to distribute.

Plus, heat pumps are a lot safer. No need to worry about gas leaks and such.

The money is well worth it, you're paying most of the cost up front, as opposed to gas heating, you pay little at the start, but pay through the nose over the years to heat your home. Its just not worth it.

Niel

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#663365 28-Jul-2012 17:57

As an intermediate, if you have the bits, try putting a 12V computer fan on top of the oil fin heater blowing down and power it with a wall plug pack. If you do not have drafts then this will very quickly heat up a whole room until you get to install a heat pump. I'm doing exactly that with our new 160 sqm home with 2x 7-fin heaters. One in the South side always on and the other in the living room only when it gets really cold (frost). I have a CPU fan that kind of clips onto the fins of my heater with just the right spacing.

Condensation evaporating causes the most cold. Try not to use the un-flued heater at all as it will make things worse the next morning.

You can never have enough Volvos!

mattwnz

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#663372 28-Jul-2012 18:35

Castleisland: We bought a 1913 villa in Mt Eden early last year.? With severe condensation issues we installed a ventilation system (having had and enjoyed one in our previous - 1990s - house).?

Now the condensation is largely overcome, but we are still cold 2 winters later.? There is relatively new ceiling insulation (+/- 4 yrs) and we are currently getting quotes for underfloor insulation (probably going with Greenstuf, professionally installed: quoted $19.50/m incl gst and installation, comments on this also welcome).

We have a flued gas fire in the tv room, an unflued wall mounted gas heater in the central hallway (that we only use when temperature in house is below 17, for short amounts of time, but would rather not use at all), other rooms heated with portable electric heaters as needed (mainly oil column heaters in bedrooms).

Have this week been given an estimate for a central heating heat pump system (about $10K), to think about alongside the quote for a single, floor mounted heat pump for the hallway ($3500).? I'm worried that heat pumps might not work successfully with the ventilation system.?? I've now been looking at other options (thanks to all the writers re heat pumps vs gas central heating!) and am yet to work out which one will work best with the ventilation system.

Any ideas/advice re this much appreciated, as we weigh up how to best pour more money into this lovely old home (- and yes, we should have looked at this prior to putting in the ventilation system!)

{MOD EDIT : SP : Moved forum}

Shouldn't the ventilation system people have recommended a heating system to you to be connected to it at the same time. The ventilation system could be making your house colder, as they can pump cold air from the roof space (which is uninsulated above the ceiling), back into your rooms. We have one of these ventilation systems that was already in the house, and turn it off in the winter due to this, as you can even fee the cold air coming in. Opening the windows for a few minutes a day does just as good a job I have found for removing condensation.
A heat pump is a good solution, but it doesn't need to be a central one. You could have two regular ones and also piping for heat transfer between rooms, which should be a lot cheaper. One thing though is they can be quite noisy, eg you can hear fans whirring when you sleep, although you probably already get that with your ventilation system.

Handle9

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#663388 28-Jul-2012 19:11

tardtasticx: We discussed this in a lecture the other day, and it was repeated over and over and over, heat pumps are the most efficient form of heating on the market today. Something like ever $1 in gets $3-4 back. So theres all this extra heat there being pushed in by this pump, imagine how much you'd have to spend on your gas heater just to get it to put the same amount into the house? More hot air from the heat pump = more hot air for your ventilation system to distribute.

Exhibit 1 of why architects are the bane of my life. Your lecturer presumes that 1kW of gas costs the same as 1kW of electricity. It doesn't, depending where you are in the country gas about 25% of the price of electricity.

Also positive pressure ventilation systems don't "distribute" air through the house. They positively pressurise the house so air wastes out through openings (cracks under doors, door seals that sort of thing). If you want to transfer heat you need a heat transfer kit but for heat pumps they are a waste of time IMO. Good for fires but a bit useless for heat pumps as heat pumps don't generally have much waste heat in a space. You aren't pumping enough kW in to heat the space. A fully ducted heat pump is a different story as you are generally going to have a supply air temp well above setpoint. High wall or floor consoles not so much.

tardtasticx:
Plus, heat pumps are a lot safer. No need to worry about gas leaks and such.

This is just plain false. A gas leak from your heat pump is a real possibility and some refrigerants are toxic. Also bear in mind that a gas installation legally must be done by a registered gas fitter. No such requirement for heat pump installations. Lots of heat pump installs are being done by guys with limited electrical registration or electricians who know nothing about refrigeration.

Anyway either solution would work much the same with the ventilation system. There is nothing all that different between the heat pump and the gas central heating system, they are both methods of tranfering heat into the space, there's no black magic which would make a difference.

tardtasticx

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#663394 28-Jul-2012 19:25

Handle9:
tardtasticx: We discussed this in a lecture the other day, and it was repeated over and over and over, heat pumps are the most efficient form of heating on the market today. Something like ever $1 in gets $3-4 back. So theres all this extra heat there being pushed in by this pump, imagine how much you'd have to spend on your gas heater just to get it to put the same amount into the house? More hot air from the heat pump = more hot air for your ventilation system to distribute.

Exhibit 1 of why architects are the bane of my life. Your lecturer presumes that 1kW of gas costs the same as 1kW of electricity. It doesn't, depending where you are in the country gas about 25% of the price of electricity.

Also positive pressure ventilation systems don't "distribute" air through the house. They positively pressurise the house so air wastes out through openings (cracks under doors, door seals that sort of thing). If you want to transfer heat you need a heat transfer kit but for heat pumps they are a waste of time IMO. Good for fires but a bit useless for heat pumps as heat pumps don't generally have much waste heat in a space. You aren't pumping enough kW in to heat the space. A fully ducted heat pump is a different story as you are generally going to have a supply air temp well above setpoint. High wall or floor consoles not so much.

tardtasticx:
Plus, heat pumps are a lot safer. No need to worry about gas leaks and such.

This is just plain false. A gas leak from your heat pump is a real possibility and some refrigerants are toxic. Also bear in mind that a gas installation legally must be done by a registered gas fitter. No such requirement for heat pump installations. Lots of heat pump installs are being done by guys with limited electrical registration or electricians who know nothing about refrigeration.

Anyway either solution would work much the same with the ventilation system. There is nothing all that different between the heat pump and the gas central heating system, they are both methods of tranfering heat into the space, there's no black magic which would make a difference.

It's common knowledge regardless that a heatpump is more efficient than any other form of heating. The output compared to energy used is much greater than all others.

Re. safety: you never hear of heatpumps being knocked off the top of a wall and killing everyone in a home, as opposed to gas leaks which can cause a whole house to explode. I know that's a bit extreme but its true. Why use gas for anything other than cooking? Plus you cant get the same level of climate control with gas as you would with a heatpump.

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Niel

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#663395 28-Jul-2012 19:35

Handle9: If you want to transfer heat you need a heat transfer kit but for heat pumps they are a waste of time IMO. Good for fires but a bit useless for heat pumps as heat pumps don't generally have much waste heat in a space.

I'm considering a heat pump and heat transfer kits, however I'll be sucking air out of the bedrooms and blow it into the kitchen behind the cupboard that is above the fridge. That way you get the stale humid air out of the bedroom and you suck the warm dry air from the lounge through the passage. If you do it the normal way by blowing air into a bedroom (and you have an aircon, not fire place chimney) then you just get a draft into the bedroom and it feels cooler as you are sucking ambient air, not heated air. Blowing air behind the fridge means the fridge runs more efficient and you cut down on exhaust noise.

You can never have enough Volvos!

Handle9

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#663398 28-Jul-2012 19:42

tardtasticx:
Handle9:
tardtasticx: We discussed this in a lecture the other day, and it was repeated over and over and over, heat pumps are the most efficient form of heating on the market today. Something like ever $1 in gets $3-4 back. So theres all this extra heat there being pushed in by this pump, imagine how much you'd have to spend on your gas heater just to get it to put the same amount into the house? More hot air from the heat pump = more hot air for your ventilation system to distribute.

Exhibit 1 of why architects are the bane of my life. Your lecturer presumes that 1kW of gas costs the same as 1kW of electricity. It doesn't, depending where you are in the country gas about 25% of the price of electricity.

Also positive pressure ventilation systems don't "distribute" air through the house. They positively pressurise the house so air wastes out through openings (cracks under doors, door seals that sort of thing). If you want to transfer heat you need a heat transfer kit but for heat pumps they are a waste of time IMO. Good for fires but a bit useless for heat pumps as heat pumps don't generally have much waste heat in a space. You aren't pumping enough kW in to heat the space. A fully ducted heat pump is a different story as you are generally going to have a supply air temp well above setpoint. High wall or floor consoles not so much.

tardtasticx:
Plus, heat pumps are a lot safer. No need to worry about gas leaks and such.

This is just plain false. A gas leak from your heat pump is a real possibility and some refrigerants are toxic. Also bear in mind that a gas installation legally must be done by a registered gas fitter. No such requirement for heat pump installations. Lots of heat pump installs are being done by guys with limited electrical registration or electricians who know nothing about refrigeration.

Anyway either solution would work much the same with the ventilation system. There is nothing all that different between the heat pump and the gas central heating system, they are both methods of tranfering heat into the space, there's no black magic which would make a difference.

It's common knowledge regardless that a heatpump is more efficient than any other form of heating. The output compared to energy used is much greater than all others.

Re. safety: you never hear of heatpumps being knocked off the top of a wall and killing everyone in a home, as opposed to gas leaks which can cause a whole house to explode. I know that's a bit extreme but its true. Why use gas for anything other than cooking? Plus you cant get the same level of climate control with gas as you would with a heatpump.

OK, lets work through your statements.

Yes heatpumps are very efficient in the right conditions. COPs of 3-4 are pretty common, which is all well and good. I buy electricity for about 26c per kWh, so each kWh of heat costs me between 6c and 8c. I buy gas for about 6c per kWh. A gas heater is around 80% efficient so my 1kW of heat costs me 7.5c, which is much the same as a heatpump.

Also as described in other posts heatpumps don't work so well in cold conditions, they can become inefficient and in some cases stop working as the coils ice up.

There is no reason that gas can't control as well as a heat pump, in some cases it will give better control. They aren't miracle devices, they are a refrigeration system with a fan on the them. Duct position plays a huge role in good control, if you don't have sufficient air throw from a ceiling duct you can't get warm air down to floor level. Gas central heating ducts are generally from beneath the floor so by default you get better air circulation and control with less of a thermal gradient through through the room.

The other issue you haven't discussed is whole of life costs. Heat pumps are generally 8-10 year life span devices gas units will often last double that.

With regards to safety with refrigeration google Tamihere cool store explosion, it'll give you some idea of what happens when refrigeration goes horribly wrong. 1 dead, 7 seriously injured.

Handle9

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#663403 28-Jul-2012 19:53

Niel:
Handle9: If you want to transfer heat you need a heat transfer kit but for heat pumps they are a waste of time IMO. Good for fires but a bit useless for heat pumps as heat pumps don't generally have much waste heat in a space.

I'm considering a heat pump and heat transfer kits, however I'll be sucking air out of the bedrooms and blow it into the kitchen behind the cupboard that is above the fridge. That way you get the stale humid air out of the bedroom and you suck the warm dry air from the lounge through the passage. If you do it the normal way by blowing air into a bedroom (and you have an aircon, not fire place chimney) then you just get a draft into the bedroom and it feels cooler as you are sucking ambient air, not heated air. Blowing air behind the fridge means the fridge runs more efficient and you cut down on exhaust noise.

It's an interesting idea, might work, it really depends how good air circulation is through your house. Quite a cool idea, I'd be interested to hear how well it works if you do do it. If nothing else you'd get air movement which would help with condensation.

The only thing I'd be concerned about is the losses you get through the ducting. Insulated duct is ok but if you have it in a really cold rood space you still can drop a degree or two on a long run. It's one of the reasons why heat transfer is rubbish in for high wall heat pump systems. If 20 degree air cools to 18 and is introduced to a 20 degree room it feels cold. It's a different story with 30 degree air from a 15kW fireplace
in a 45m2 room.

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#663406 28-Jul-2012 19:57

Niel: As an intermediate, if you have the bits, try putting a 12V computer fan on top of the oil fin heater blowing down and power it with a wall plug pack. If you do not have drafts then this will very quickly heat up a whole room until you get to install a heat pump. I'm doing exactly that with our new 160 sqm home with 2x 7-fin heaters. One in the South side always on and the other in the living room only when it gets really cold (frost). I have a CPU fan that kind of clips onto the fins of my heater with just the right spacing.

Pictures or it didn't happen, please?

tardtasticx

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#663408 28-Jul-2012 20:01

Handle9:

OK, lets work through your statements.

Yes heatpumps are very efficient in the right conditions. COPs of 3-4 are pretty common, which is all well and good. I buy electricity for about 26c per kWh, so each kWh of heat costs me between 6c and 8c. I buy gas for about 6c per kWh. A gas heater is around 80% efficient so my 1kW of heat costs me 7.5c, which is much the same as a heatpump.

Also as described in other posts heatpumps don't work so well in cold conditions, they can become inefficient and in some cases stop working as the coils ice up.

There is no reason that gas can't control as well as a heat pump, in some cases it will give better control. They aren't miracle devices, they are a refrigeration system with a fan on the them. Duct position plays a huge role in good control, if you don't have sufficient air throw from a ceiling duct you can't get warm air down to floor level. Gas central heating ducts are generally from beneath the floor so by default you get better air circulation and control with less of a thermal gradient through through the room.

The other issue you haven't discussed is whole of life costs. Heat pumps are generally 8-10 year life span devices gas units will often last double that.

With regards to safety with refrigeration google Tamihere cool store explosion, it'll give you some idea of what happens when refrigeration goes horribly wrong. 1 dead, 7 seriously injured.

How do you get your gas? Is it piped in or do you use tanks?

If you get the right type of heat pump, you wont need to worry about that. Most top range ones work fine in cold conditions, if you're going to buy a heat pump for your house you really shouldn't be cheaping out anyway.

Plus, that is in no way relevant, that was an industrial accident, given we are talking about residential use here. I could go on endlessly about the amount of industrial gas disasters that have happened over the years, but when talking about residential use, theres next to no comparison

stuzzo

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#663411 28-Jul-2012 20:14

At the risk of raising the ire of some of my fellow Geekzoners I might point out that the gas is a CO2 emitter and the electric based heat pump is much lower based on our 80% low carbon electricity supply.

Handle9

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#663413 28-Jul-2012 20:15

tardtasticx:
Handle9:

OK, lets work through your statements.

Yes heatpumps are very efficient in the right conditions. COPs of 3-4 are pretty common, which is all well and good. I buy electricity for about 26c per kWh, so each kWh of heat costs me between 6c and 8c. I buy gas for about 6c per kWh. A gas heater is around 80% efficient so my 1kW of heat costs me 7.5c, which is much the same as a heatpump.

Also as described in other posts heatpumps don't work so well in cold conditions, they can become inefficient and in some cases stop working as the coils ice up.

There is no reason that gas can't control as well as a heat pump, in some cases it will give better control. They aren't miracle devices, they are a refrigeration system with a fan on the them. Duct position plays a huge role in good control, if you don't have sufficient air throw from a ceiling duct you can't get warm air down to floor level. Gas central heating ducts are generally from beneath the floor so by default you get better air circulation and control with less of a thermal gradient through through the room.

The other issue you haven't discussed is whole of life costs. Heat pumps are generally 8-10 year life span devices gas units will often last double that.

With regards to safety with refrigeration google Tamihere cool store explosion, it'll give you some idea of what happens when refrigeration goes horribly wrong. 1 dead, 7 seriously injured.

How do you get your gas? Is it piped in or do you use tanks?

If you get the right type of heat pump, you wont need to worry about that. Most top range ones work fine in cold conditions, if you're going to buy a heat pump for your house you really shouldn't be cheaping out anyway.

Plus, that is in no way relevant, that was an industrial accident, given we are talking about residential use here. I could go on endlessly about the amount of industrial gas disasters that have happened over the years, but when talking about residential use, theres next to no comparison

Our gas is reticulated.

Even the "top of the range heat pumps" don't work fine in very cold conditions. I can point to a number of very large commercial sites, using brands which are considered top of the range, which have had serious problems with heat pump systems not working properly in very cold conditions. These are brand new sites where heat pumps were the wrong solution because of the ambient conditions.

You were making the claim that heat pumps were completely safe and gas was dangerous, it's not accurate. Properly installed both systems are safe. Incorrectly installed both systems are dangerous, especially with some of the idiots out there installing heat pumps.

I don't have a problem with heat pumps, I have one in my house, it works well and we are considering another one. To make blanket statements that heat pumps are better than gas isn't accurate. Each technology has it's place but they should be considered on their merits for the use case, not on some blanket statement that one is superior for all use cases.

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Snowflake

#663448 28-Jul-2012 22:18

Castleisland: We bought a 1913 villa in Mt Eden early last year.? With severe condensation issues we installed a ventilation system (having had and enjoyed one in our previous - 1990s - house).?

Now the condensation is largely overcome, but we are still cold 2 winters later.? There is relatively new ceiling insulation (+/- 4 yrs) and we are currently getting quotes for underfloor insulation (probably going with Greenstuf, professionally installed: quoted $19.50/m incl gst and installation, comments on this also welcome).

We have a flued gas fire in the tv room, an unflued wall mounted gas heater in the central hallway (that we only use when temperature in house is below 17, for short amounts of time, but would rather not use at all), other rooms heated with portable electric heaters as needed (mainly oil column heaters in bedrooms).

Have this week been given an estimate for a central heating heat pump system (about $10K), to think about alongside the quote for a single, floor mounted heat pump for the hallway ($3500).? I'm worried that heat pumps might not work successfully with the ventilation system.?? I've now been looking at other options (thanks to all the writers re heat pumps vs gas central heating!) and am yet to work out which one will work best with the ventilation system.

Any ideas/advice re this much appreciated, as we weigh up how to best pour more money into this lovely old home (- and yes, we should have looked at this prior to putting in the ventilation system!)

{MOD EDIT : SP : Moved forum}

i'm also in mt eden, a 1920 bungalow. underfloor insulation made a HUGE difference. brought the ambient temperature in the house up from 8-10 to about 15 in winter time. its also cheap too as you can get the govt insulation subsidy. i had mine installed by underfloor.co.nz and can recommend them. i went for the cocoon r2.6 stuff, probably the same sort of insulation as the greenstuf.

i also put in a central gas system for around $8k. i didnt bother with a ventilation system, and since having the central gas system blow air all around, the house hasnt been damp since. I ran a dehumidifier for two days a week ago, and it only collected about 1 litre of water. we dry clothes inside all the time too. before the central, we would have emptied the dehumidifier at least once a day - now it just gathers dust. i considered the ventilation systems, but decided that central gas was a better use of funds..

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