Dreadnaught

Here is a blog post on overheating that might be of interest for those designing an highly insulated house: https://elrondburrell.com/blog/passivhaus-overheating-design/. I am adopting its lessons in my design.

For a passive house, overheating in summer is generally the greater risk than an inadequacy of heating in winter. Best practice: first step is to design-it-out to the extent possible (<2% ideally), then consider other solutions, including active cooling. I recommend The Passivhaus Handbook by Janet Cotterell if anyone's interested. Chapter 7 & 11 discuss overheating at length.

Fair challenge. Its not about elimination of all overheating in all circumstances. Zero % overheating is unrealistic, as you say. I am referring to optimisation at the time of design. PHPP presents an average % of hours overheating per year, defined as a temperature over 25ºC. The standard for certification requires a modelled figure of 10% or less. Most aim for below 5% and I prefer below 2%. Architectural design optimisation of overheating is effective for this, as I am finding. Oh and I plan to have the option of an air conditioner, should it prove required.

Ah, the bat to eat the flies and moths, clever tactic. I like it.

True. Evening and night tends to be worse: moths, mozzies and worse.

Oh, and if you are playing with the summer overheating % in PHPP, as I am at the moment, there is a new advanced shading sheet available from Peter Warm. Warm said we are the first to be using it in the UK. It enables better modelling for transparent shading objects, such as trees. Useful for me because I have whopping horse chestnut slap bang between my new build and the southerly sun and about half a meter from my boundary.

Purge is good but I hate flies (and moths at night). Any purge windows I have will need fly screens. As Jae Cottrell once told me, fly screens also help marginally with shading.

Oh yes, on summer bypass, some MVHR models have "simulated" bypass. The Paul Climos 200, which I rather fancied, has this. As far as I can tell, this means it shuts down extract. It does not actually have a physical bypass of the heat exchanger. I assume the heat exchanger assumes you will open a window for the extract, which makes some sense. I am not sure how this can be called "simulated" but that's another matter. As I don't want to open windows if I can avoid it, this means I will be choosing another MVHR model.

Some observations. Designing out cooling is quite easy and effective. I am doing it now with PHPP for my build. As mine is a modern house, I have more freedom to play with window sizes and architectural features, such as overhangs. Floor to ceiling glass is to be avoided and I am doing so in my build. The glass below knee height offers little extra light but much extra heating gain. Building regs require an openable window in every habitable room for purge ventilation. I wish it didn't, I don't want them in my modern house as it it does not have any conventional windows, just large frameless roof lights and architectural glass. Problematic. Purge ventilation is sometimes defined as 4 air changes per hour (ACH). Most MVHR work at about 0.4 ACH. Trying to achieve it with an MVHR will lead to hugely over specifying the MVHR and require much bigger ducting. I know, I tried. The MVHR I needed was 271 kg! Using water UFH for cooling delivers that cooling in a sub-optimal place, the floor. Sub optimal for convection. And if not carefully controlled can cause condensation. I decided against it. In the end, I plan to put in a conduit for a split air conditioner in case I need it in my Passive House. Because split air conditioner are highly common they are very very cheap in comparison (about £800 tops) and finding someone to install or service it will be easy I imagine. I will try the house for a year and install an air conditioner if I need one. Its easy to over engineer the solution and get carried away. I am aiming for a very simple, as simple as I can make it and for it to be cheap, and maintenance free.

Oh, and if cooling is needed, first it shouldn't be much as it should be designed out at PHPP stage, but if it is needed then just install an £800 air-to-air split unit air-conditioner. (I will put in place a conduit and wiring for one just in case.)

For a passive house, isn't the simplest and lowest maintenance the following… E7/E10. No gas, no PV* Sunamp for DHW electric UFH cables embedded throughout the slab (not just bathroom) for space heating Big difference is no wet UFH. What's wrong with this? * I have huge tree blocking the sun.

@PeterStarck, why do you say "in a PH larger than 130m2"? Wow, Peter, you have really got me thinking! I am thinking whether I really need wet UFH. How about simple electric UFH instead across the whole house as you also reminded me of something @TerryE said a while ago. Until your comment my plan was wet UFH and SunAmp eDual with E7/E10. But @TerryE's reasoning, which I have just remembered, is (to invent a quote) "don't store heat energy in a Sunamp and later transfer it into the slab. For a Passive House, where the diurnal temperature fluctuation is minor so the time of day of heating doesn't matter much, just put the heat straight into the slab according to the E7/E10 timetable, the slab will release the heat gradually in to your home." Thus, if I went with electric UFH then this would make my system even simpler. Just E7/E10, a SunAmp for DHW, and electric UFH for space heating. Simple as can be. Like you, I like simple. (However, with no wet UFH I would lose the chance to add an ASHP later if my heating demand turned out to be higher than I expected.) (Mine will be 117m2 TFA Passive House*. I can't have PV because its behind a huge tree . I am currently at the stage of PHPP modelling.) * hopefully certified, am working on it.

Looks fabulous. How do they fish out the spiders in the end without leaving footprints?

For me planning a near-passive-house new build, the following quote suggested that a SunAmp model with UFH pump and maybe other parts of a UFH circuit included (I suppose an expansion vessel is unlikely?) may be arriving soon. A potential central-hearting system in a box. Could be ideal for my needs. "Forthcoming availability: Fully-integrated Sunamp HydrobloQTM incorporating system pump and other hydraulic functions". Source for quote, https://www.sunamp.com/wp-content/uploads/2018/06/Leaflet-1-Sunamp-Dual-Port-Heat-Stores-Technology-Description-final.pdf

Welcome. I have learnt a huge amount by reading the answers to others questions, so I look forward to yours.

As far as I have read, air-based ground-source heat-transfer systems suffer from nasty microbial things living within the underground pipes. One correction. As was mentioned long ago by @JSHarris, at the depth of those pipes they are not tapping geothermal energy (from from the original formation of the planet and from radioactive decay of materials). Its heat from sunlight that has warmed the ground and soil beneath. Top down not bottom up. I also wonder if the irrigation water would be from a sustainable source.

A UK supplier of Nickel Iron batteries? https://www.bimblesolar.com/batteries/nifebatteries

@JSHarris Nickle Iron?

Superb. Exactly what I am planning. Did you put them anywhere else? Did you try them in any ceilings (I am tempted)? I wonder did you use a lighting designer is this your own inspiration?

Wow, that looks great, @lizzie! @lizzie, in the second photo, what are those linear recessed lights? I am after something just like that. And is that a sun pipe?

Oh, are they crappy. I was thinking of copying @lizzie and using those on my build. Why crappy?

And try this link for your personal email settings: https://forum.buildhub.org.uk/notifications/options/.

I have had the opportunity to drink beer much older than that (more than 10-years in fact) and it has been fine.

Impressive progress. My plot will need piles so i'd appreciate the chance to visit on the 17th July, if that's possible.

For ease of reference, (current) list of timber-frame companies exhibiting at NSBRC https://www.nsbrc.co.uk/exhibitor-search/?category=Timber+Frame.