Dreadnaught

Could there be a control system that attempts to anticipate when the windows are open (exceptionally low back pressure) and reduces fan speed? I have seen a heating systems that tries and identify when a window is open and reduces the heating load to save energy. Just a guess.

At the risk going off topic, I was in CostCo today. Do we really need all built-in appliances any more. For an oven, a worktop halogen oven (<£40). For a hobb, worktop portable induction pads (<£50 each, have a few). Perhaps not for everyone but I'm tempted. A positive article on halogen ovens: https://www.independent.co.uk/life-style/food-and-drink/features/how-i-fell-in-love-with-halogen-ovens-2098619.html.

Ben Adam Smith, of the House Planning Help podcast and coming towards the end of his own build, posted this on twitter yesterday:

PC (or PC sum) = a prime cost sum is an allowance for the supply of work or materials that will be nominated by the client.

I am no expert but you might find this podcast interesting. Ruth Butler, the owner of the building but also an architect herself, discusses her contracting approach, which was to allow the contractor are margin but not give him any flexibility to choose items. You could possibly use her approach. By the way, I have visited her finished home in Sussex. Well worth a visit if you are in the area. http://webuildacademy.libsyn.com/ruth-butler-why-ruth-went-passivhaus

TMV = thermostatic mixing valve: a valve that blends hot water with cold water to ensure constant, safe shower and bath outlet temperatures, preventing scalding.

Don't have a house yet. My house is on the drawing board. Need to decide what to buy for it. Oh? What does £20 buy?

Some thoughts on enthalpy heat exchangers: Inside humidity typically only really becomes a problem in the heights of summer or the depths of winter In the depths of winter, the cold conditions lead to very low amounts of water in the outside air I have heard of people rejecting the entire Passive-House concept because of low inside humidity in the depths of winter, causing nose-bleeds with family members, etc. This is often caused by too much air flow and nothing to do per se with not having an enthalpy heat exchanger. Once air-flow rates are adjusted the problem usually goes away For sensible heat, efficiencies of heat recovery can be as high as 95% for good normal models. For an enthalpy heat exchanger, the efficiency of sensible heat exchange is reduced, often to around 84% For an enthalpy heat exchanger, the efficiency of latent heat recovery is only about 65% in the best cases as far as I have seen, not higher For an enthalpy heat exchanger, the combined efficiency figures often exceed 100%. That is, it reduces the consequent evaporative cooling indoors required to re-atain an equilibrium level of humidity An enthalpy heat exchanger will reduce fluctuations in the inside humidity level in relation to that outside, nothing more But, based on what I have said, this increased stability will only lead to more perceived comfort at the extremes And its not a magic bullet. Internal humidity will still be a complex product of the changing balance of sources and sinks of moisture combined with the effects of moisture added or removed by ventilation Given all this, I am unsure whether its worthwhile getting an enthalpy heat exchanger. As always I am concerned foremost with comfort, not energy. And the cost does not matter either. Will I notice a difference with having an enthalpy heat exchanger or not? Is it worth it to cater for the occasional day in mid winter or mid summer? I don't know. The geek inside me wants one; the realist resists. Views?

I will need to do all my drying inside the house. I'm adding one of those ceiling drying rails in my laundry room. I have limited outdoor space. I considered a MVHR linked drying cupboard and would still like one. My PHPP assumes 3.5 kWh of useful energy per drying event and 57 such events per year. About 200 kWh in total of cooling per year. Not much.

My observation was from this quote "Usually activates based on automatic external temperature point e.g. 21°" from this document from Zehnder, https://www.zehnder.co.uk/download/102348/en_uk-63373.pdf. They might have been simplifying.

To swap the heat exchanger is quite a few hundred quid I think but if you buy the enthalpy exchanger when you buy the MVHR, the marginal cost is a lot less, about £2 - £300 I think. Some models, like the Paul Climos 200, come with the enthalpy exchanger as standard. Swapping by the way is usually a trivially easy procedure. I am exploring how enthalpy-exchanger-based MVHRs are treated by PHPP. For sensible heat, an enthalpy heat exchanger is less efficient than a normal one. Say 84% compared with 94% for a normal one. But once latent heat is included, overall energy efficiency of the enthalpy heat exchanger exceeds that of a normal one. I am not sure whether that is fairly represented in PHPP. Commonly, humidity (the moisture content of the air) complicates simple energy calculations and is often overlooked.

In reading the specification of some MVHR units, some seem to trigger the summer bypass solely on the basis of an external temperature. Some seem to be based on a algorithm linked to internal and external temps. I wonder if any take notice of humidity or other characteristics. (And, as mentioned before, some don't have a summer bypass at all. And instead say they have a "simulated" one, which as far as I can tell means simply turning off the extract fan).

Except for evaporative cooling, for example by drying clothes indoors. Such incidental evaporative cooling is modelled in PHPP. More generally, humidity is worth considering when considering comfort and energy. One thing I am evaluating is having an enthalpy heat exchanger in my MVHR.

@Russdl what are your further thoughts about certification, why was your other-half keen? And what is your house like?

From the numbers, that looks like a very nice balanced build, @MikeSharp01. What is the form factor? I am guessing close to 2.5. I fully agree with your point about PHPP being a balancing act and all the better for it, in my opinion. On certification, beware that you require a lot of photos of the build and other docs, which you may have, as referred to in Warm's design checklst: http://www.peterwarm.co.uk/?dl_id=35.

In this earlier video on his plastering, he mentions that the interior plastering is more like a two layer render, for a nice texture, and being really good for the airtightness. He wanted to avoid dead flat surface and sought a slight "rub" to the texture. A scrubbed sponge finish with different textures on the walls and ceilings. He seems to have been experimenting. I suspect he's regretting it now.

@Russdl I would love to and will do so if I can. But because of planning constraints, the form factor of my planned home will be very poor (4.6) and so we are struggling a little. Its a modern bungalow with lots of roof windows but behind a tree. It may come to the point where the compromises are just too great (or too expensive) to make it under the thresholds to get certification, in which case we will almost be there and instead I might go for the lower certification (the PHI Low Energy Building Standard). Irrespective, I will proceed in the design and build as if we are going for Classic certification, with the air tests and rigorous attention to detail as, in my opinion, that is what brings a comfortable home.

@MikeSharp01 do you go for certification? When you were modelling in PHPP, what were your areas of focus? Form factor, shading, window positioning, overheating, energy use? Where did you come on the key parameters?

Blimey, I did not know this could happen to plastering, and from Mr Charles Luxton himself. What was the cause? How can this be avoided?

And my reply to @Russdl. ~~~~~ I was tempted to do the PHPP myself but in the end I got an expert to do the first version for me. My expert is from one of the timber frame companies. Compared to some, he's quite good value, which is why I used him. And also I liked that he does PHPP every day of the week, compared to some "experts" who don't. I agree PHPP is quite intimidating and it took my a few days to get my head around it. I have done quite a lot of other modelling in the past so am comfortable with spreadsheets. From now on I think my expert and I will work together as a team as we develop the design with me spending as much time with my nose in PHPP as he does.

Send a message to a mod, such as @JSHarris or @Nickfromwales. They will turn on the functionality for you.

@Russdl and I were just discussing PHPP in a private discussion and we wondered who on BH has experience of actually using PHPP to design a house. I know @PeterStarck did his own calcs, and he was kind enough to show them to when I visited his splendid build in East Kent. Who else has a PHPP model for their house, or is preparing one? (For those wondering, PHPP is the Passive House Planning Package, a huge and complex spreadsheet for calculating the thermal and other characteristics of a building, produced by the Passive House Institute in Germany and available to buy for about £200. It is a requirement for a certified Passive House. More info here: https://passipedia.org/planning/calculating_energy_efficiency/phpp_-_the_passive_house_planning_package.)

Another idea, could those who welcome visits add it to their signatures or "about me" sections? Would that help? I have visited four BH members so far, from whom I have learnt a huge amount. I am immensely grateful for their generosity and hope to return it to the community when I am in a position to do so.

Yes, I agree. I have come across two recent examples of well-inslulated recently finished builds that are overheating. One was modelled in PHPP and one was not. Some don't take overheating seriously enough at design stage. The 10% of annual hours over 25ºC that is part of the passive-house standard is, in my and many other people's views, far too high. I would like to see a limit of 5% or even 2%. For me, passive house is foremost about making a lovely comfortable home. Time over 25º, let alone any time near to 30º, needs to be considered and minimised. Working through PHPP for me has been a revelation. As the saying goes, "all models are wrong, but some are useful". I have found PHPP to be immensely useful in making me think about the things that are important. I had read about PHPP extensively before modelling my own house. Even so it has exceeded my expectations.

Agree. For example, in my design when I swapped from a hot water tank to a Sunamp, with its much lower heating losses, that change alone reduced my modelled annual over-heating rate by two full percentage points. Agree. For me that will be a simple and comparatively low-cost split air conditioner in the large double-height living room. I might also go for a second indoor unit in the master bedroom too (you can have up to 5 indoor units as I understand), not sure yet. I might try and build the indoor unit(s) into the ceiling as I have void where they could fit. I think it could look quite good.