GSHP vs PassivHaus

anon_ymous

The average COP of a GSHP is around 4.5. I require 15000 kWh of gas for the year or 3333 kWh with a GHSP. Both a GSHP and PassivHaus cost around £30K but Crucially you can keep "adding on" to a retrofit PassivHaus. You don't need 30K upfront or via a loan. My house is 120 square metres 

At 15p/kWh  that's around £500 for the year in running costs

At 35.4p/kWh that's around £1180 for the year in running costs 

At 54p/kWh that's around £1800 for the year

A PassivHaus retrofit requires you to use equal to, or less than 25kWh/square metre. That's 3000 kWh

At 3p/kWh (gas) , that's about £90 a year

At 10p/kWh (gas), that's about £300/year

At 15p/kWh (gas / old electric price), that's £450 for the year

At 35.4p/kWh (electric), that's £1062/year

At 54p/kWh (electric), that's £1620/year

So even without a heat pump of any kind, a PassivHaus wins pretty much hands down both on financial "ease" and actual costs.

There's nothing stopping you from getting a heat pump even after going for a PassivHaus though I imagine if you do go down the retrofit PassivHaus path, you'd probably get an ASHP because whilst the COP is just 2.8, they are considerably cheaper than a GSHP and you've already made your house much cheaper to run even without a heat pump

Of course if you're going for an ASHP, the biggest advantage of an ASHP is that it is considerably cheaper to install than a GSHP and you aren't necessarily thinking whether it's better for you to have a PassivHaus instead

Food for thought anyway. My intended path is the PassivHaus route, and if I then want I'll just get an ASHP 

markin

A single air to air heatpump would do, or even mostly be used for cooling after getting near to PassivHaus and just heat water with an immersion/ solar diverter, and the credit from selling power.

The goal now is to make houses make more power than the house uses, making it net positive.

Screwdriva

waqasahmed said;

Both a GSHP and PassivHaus cost around £30K….

I admire the enthusiasm but would suggest some research on actual costs of both.

If you do not need to bore deep into the ground, a GSHP will cost around £15K (don’t forget to factor in the £6K BUS scheme grant). But you will need 350-400 sq metres of sunny lawn to lay down the insulated piping for it to work. 

An EnerPHit (Passivehouse retrofit) certification is not easy to achieve. The insulation materials & triple glazing alone would take that cost well above £30K.

markin

I'm sure he meant they both cost 30K each, You don't really need both do you? One or the other.

£15K for external insulation
£10k for triple glazing?
£2-3K to insulate the floors
£3K for a small MHRV, mainly for kitchen and bathroom

But then £6K for Solar, And £3-6k for batteries, Or £10k for a Powerwall 2

???? Profit!

Not many bother with the certification, The Sap/ standard energy certification will look great when selling, If they every plan too, And doing blower test is nice but not needed is it?

anon_ymous

markin said:

I'm sure he meant they both cost 30K each, You don't really need both do you? One or the other.

£15K for external insulation
£10k for triple glazing?
£2-3K to insulate the floors
£3K for a small MHRV, mainly for kitchen and bathroom

But then £6K for Solar, And £3-6k for batteries, Or £10k for a Powerwall 2

???? Profit!

Not many bother with the certification, The Sap/ standard energy certification will look great when selling, If they every plan too, And doing blower test is nice but not needed is it?

Essentially this. Also I did consider the fact that I'd need a bore hole 

anon_ymous

markin said:

A single air to air heatpump would do, or even mostly be used for cooling after getting near to PassivHaus and just heat water with an immersion/ solar diverter, and the credit from selling power.

The goal now is to make houses make more power than the house uses, making it net positive.

That's fair. I'm sorting the solar bit out first and then I'd go further 

An ASHP once at the end is "nice" but not necessarily needed 

Reed_Richards

markin said:

I'm sure he meant they both cost 30K each, You don't really need both do you? One or the other.

£15K for external insulation
£10k for triple glazing?
£2-3K to insulate the floors
£3K for a small MHRV, mainly for kitchen and bathroom

This all seems incredibly cheap if you include labour costs.  Lets take the floor insulation:

1. Room-by-room, remove all the furniture and take up the floor covering.
2. Remove skirting board
3. Level floor with additional 50 mm layer of screed?
4. Add 200 mm (say) of insulation board
5. tape joints
6. Cover with MDF board or similar
7. Chop 260+ mm off the bottom of the door
8. Replace skirting board at new height
9. Relay floor covering and replace furniture
10. Raise any light fittings that now hit your head because of the reduced height
11. Replace all entrance doors with shorter ones.  Possibly install ramps to cope with the new step into the house.

That's a lot of work and a lot of labour costs.
  

Reed_Richards

markin said:

£15K for external insulation

This is a timber frame house.  I'm pretty sure insulation applied externally would not insulate.  We've discussed this previously.  

markin

I don't know any details on his house, But in general the most common i would think is a house with a small crawl space with a suspended timber floor, all you need is to make a hole to get under, The is even a company with a robot that will spray foam it, if that's needed.

On solid floors obviously you need to dig it out and lower it for insulation and new screed, And yes the costs would quickly rise on that even if you DIY.

anon_ymous

markin said:

I don't know any details on his house, But in general the most common i would think is a house with a small crawl space with a suspended timber floor, all you need is to make a hole to get under, The is even a company with a robot that will spray foam it, if that's needed.

On solid floors obviously you need to dig it out and lower it for insulation and new screed, And yes the costs would quickly rise on that even if you DIY.

So it's a timber frame with solid floors (according got the EPC) 

Screwdriva

markin said:

I'm sure he meant they both cost 30K each, You don't really need both do you? One or the other.

£15K for external insulation
£10k for triple glazing?
£2-3K to insulate the floors
£3K for a small MHRV, mainly for kitchen and bathroom

But then £6K for Solar, And £3-6k for batteries, Or £10k for a Powerwall 2

???? Profit!

Not many bother with the certification, The Sap/ standard energy certification will look great when selling, If they every plan too, And doing blower test is nice but not needed is it?

I'm helping an acquaintance with their EnerPHit retrofit for a 2000 Sq Ft detached house. Safe to say, costs are currently in the six figure range, and rising rapidly. I had suggested a Vaillant GSHP for heating but they are waaay over budget & just under the ideal 3X garden area (vs. living area) for the pipework, so they decided to go with a Vaillant AroTherm+ via a heat geek elite installer instead.

Here's a snapshot of what takes to achieve PassiveHouse certification. £30K wouldn't cover the cost of the triple glazing needed.