Improving insulation to suit an Air Source Heat Pump - what are you doing?

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. 

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.

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!

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.

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.

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?

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.

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.

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.

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: