Depends on the design temperature for the radiators. They can run at same flow temperature as UFH if large enough. But usually you will blend lower for UFH. 

So would it be possible to run one room of UFH off a radiator system ? Excuse my ignorance !

Yes, @juliamc - you can mix the systems. They are slightly different ways of running the pipework. Radiators are usually fed from a pair of parallel pipes that run from one position to the next. UFH pipes are run from a central location called the manifold.

I’ve put lots of photos in the article on Underfloor heating (part 2).

Your questions are perfectly valid. Far too few people know about the possibilities and the pros/cons of each approach.

If you have questions specifically about UFH, then ask them out there in the open part of the Forum. That enables others to learn too.

Sorry, I should have put the question about RetrofitWorks here: are they going to offer any advise about getting further works to the house etc.

For example… I have a fireplace/chimney bloke coming next week to advise about blocking up the chimney, but he’s not an insulation specialist. I know the chimney should remain ventilated but I don’t want draughts blowing into the living room. What should I be asking him to do? 

Good question, @juliamc - this might’ve been missed. Let’s ask the one and only @Transparent, as well as fellow trialists, @Rob Whitney @RAJ (not seen much from you, how’s it all going?) @hydrosam @Gingernut49 @mrmojorisin04 - thoughts welcome!

I was emailed a comprehensive booklet detailing all the additional works they recommended I have done after the installation. Some didn’t make sense, such as changing my double-glazed windows to triple-glazed but then improving ventilation by adding trickle vents in the kitchen and bathroom. I already have extractor fans in both: automatic in the bathroom and one I can turn on in the kitchen when I’m cooking.

My house is full of draughts which can definitely be considered uncontrolled ventilation:  bad seals around the double glazed windows, holes behind boxing in the loo and bathroom where ‘any old builder’ (or plumber) has put a waste pipe through and not sealed it properly just boxed it over, even holes in the ceiling where dust and wasps get into the light fittings. If all those were fixed I’d need controlled ventilation to get some oxygen in. I’d gladly have that done but who to get to do it ?

What’s the latest thought about trickle vents @Transparent ? I think the Retrofit bloke said they weren’t thought to be the answer these days.

Thanks @Transparent for the link about the Chimney Sheep ! I have had the flue inspected and measured by my chimney and fireplace expert and he’s fitting one for me, with a new cap on the chimney top to balance the up draught (or words to that effect).

Now all I need is someone to deal with everything else.

Retrofit were particularly unhelpful in that respect, saying everyone’s booked up for the next 6 months. I understand that but how would I ever get on their list if I don’t know who they are ???

@Tim_OVO ‘smart home trials’ did respond but only to say they can’t help and will see if Retrofit can.

Very frustrating.

Trickle vents: @Gingernut49 wrote:

improving ventilation by adding trickle vents in the kitchen and bathroom

I’m puzzled by this.

If we were contemplating a New-Build house, then you would be unable to achieve the minimum requirement for energy efficiency (the SAP score) if trickle vents were stipulated. Yes, I know they are still being fitted by the major housing developers such as Bovis/Vistry, but that’s due to a loophole in the law by which they are not required to apply the current standards.

To add ventilation to a house, I would be recommending a small heat-exchanger MVHR unit (Mechanical Ventilation with Heat Recovery).

These are now available sub-£300 for use in just 2 or 3 rooms of a house. Here’s the HR100 from Vent Axia:

It has 5 ports:

• fresh-air input from outside
• warmed fresh air to living area(s)
• stale/humid air from bathroom & kitchen
• stale-air to outside after heat has been extracted
• 19mm condensate drain to outside

Here’s one I fitted in a garden-office about 6 years ago. This is positioned above a doorway to the en-suite toilet area. It is therefore the “bottom opening” version so that the heat-exchanger element can be removed from below and cleaned out once a year:

The Vent Axia HR100 has standard 100mm diameter connections. I used a combination of rigid and flexible pipes to squeeze everything into the small space above a suspended ceiling.

Houses with MVHR units can operate on a lower setting than the usual 15-litres/sec air extraction rate because they work continuously. See Building Regulations Part-F for information.

@Transparent my energy report from Retrofit strongly recommended ventilation in my house: humidity controlled extractors in kitchen and bathroom as the least cost option (their estimate £300 per room) which wouldn’t effect the energy rating of course.

MVHR estimated at £4000 or Demand Controlled Ventilation at £3000 were itemised in the appendix of the report for information. I’m keen to investigate the MVHR option, but will I ever get a follow-up from Retrofit to advise me who can do it??

So I presume that Retrofit aren’t expecting that they will be paying for your MVHR out of the £5000 insulation allocation for each house?!

The heat-exchanger unit itself for a “whole-house” installation would typically cost around £1100-£1600 depending on the quality of the fan motors and the exchanger plates.

 I’ve added an additional radiator within my unit with water fed from the same thermal store outlet that supplies my underfloor heating.

The 150x150mm mini radiator is normally used by PC gamers for their water-cooled processor chips and graphics cards. I screwed it inside the heat-exchanger case immediately before the outlet supplying fresh air to the house. The input/output ports take ½-inch flexible hose which run through a couple of rubber grommets in the side-wall of the enclosure.

The main cost of a whole-house ventilation system is the running of the pipes themselves. Without taking up floorboards to work out how the pipes might be inserted I don’t see how it’s possible to give a price estimate.

Beware that many firms leave the pipe-runs to be installed by the most junior member of the team. That means he/she may not appreciate the need for:

• sufficiently air-tight seals between joints
• rigid (not flexible) pipe where possible to maintain pressure
• adequate insulation around all pipes, especially at bends
• the use of round pipe rather than rectangular to reduce noise
• no pipe joins within 4 pipe-diameters of an outlet vent
• not sawing through the odd joist(!) to reach a tricky location

And that’s why I’ve installed everything myself so I know it’s optimal!

@Tim_OVO  do you want to lift this post into the main open Forum?

Haha !! that would be good wouldn’t it !!! No. The £5000 insulation allocation (if it was actually divided up like that - news to me) has all gone on the heat pump, radiators, cylinder and many yards of plumbing - plus the hours of work needed to install it. Their report included information like this, ie further works that could be done in an ideal world. We’re not living there are we?

There should be an additional-works budget for each house beyond the actual heat-pump hardware and its installation.

Most of that would likely be allocated for upgrading insulation. But whatever it’s spent on, it must be accounted for. The final report to BEIS will be almost useless if it doesn’t show what additional work was undertaken - including extra stuff paid for by the homeowner.

@Transparent would you consider my warm air ducts could be repurposed for MVHR ?

Yes of course. They’re bigger than the 100mm most commonly used for MVHR, but that shouldn’t a problem. The slower the air moves through the duct, the less noise it makes.

@Transparent you read my mind! But this great info is in amongst a thread that’s specific to the trial. You might consider copying and pasting the good stuff into a new topic which we can post here…..?

Done. The basic shell is here.

I’ll add a header-image and a couple of diagrams later. But at least Trialists here can now direct others to the relevant topic on the open Forum.

update on the chimney… the ‘sheep’ has been installed with a new sailor’s hat chimney pot ! No more draughts.

This topic is now in the public Smart Home category and ready to help anyone interesting in decarbonising their home’s heating with a heat pump. 

Please be advised, some comments in this thread refer to trials that OVO are involved in, with households of a trialist getting an air source heat pump. We have a private forum area for trialists to discuss their heat pump. If you’re a trialist and you want access, let us know here: