giacomo_z

@Iceverge I like your practical approach in my case, as this is a retrofit and I can take a piecewise approach. For a new design, perhaps I can answer my own question. Although the ventilation requirements for wet rooms don't take into consideration the size of the room, the relative humidity of a big room will be less than a small room because the sources of humidity (shower, bath, hob, etc) are constant - ultimately a bathroom will normally have up a 22mm hot water pipe supplying it. Therefore, the absolute amount of air to be changed per hour to bring the relative humidity down in a big room will be less than in a small room. For bedrooms, once again it's unlikely than more than 2 people will sleep in a single bedroom, regardless of the size.

@Iceverge and @JohnMo thanks for your comments. The problem I have is that most rooms are wet. My house is as follows: The wet rooms - kitchen, bathroom, ensuite and possibly cloakroom 3 bedrooms - I get condensation overnight and air is very stuffy in the morning. DO I treat these as wet as well then? Dining/living room - this is the only place where I can hang clothes to dry on an airer in winter. Obviously, condensation forms on the windows Hallway and landing are possibly the only dry areas Regardless of the route I decide to take for my particular house, my doubt stands. Have I interpreted Table 1.2 and 1.3 requirements wrongly? I would appreciate if anyone had any pointers on my calcs. Thanks

I am in the process of designing mechanical ventilation for my 20-year old house, which is not particularly airtight. My goal here is to improve air quality and reduce condensation automatically - without having to worry about opening trickle vents or windows. I am aware this will have a cost in terms of running cost of the unit itself. Note the exercise below assumes a perfectly airtight house, with no leakage. This is hardly true for my house but again the goal here is not improving airtightness but rather air quality. Now, part F requirements, as I understand them, say that: There should a be a minimum whole house flow rate of 0.3 l/(s.m2) Specific rooms should have a flow rate according to Table 1.2: Kitchen 13 l/s Utility room/bathroom 8 l/s Also from Table 1.3, I understand bedrooms should have flow rate of 6l/s I don't understand requirements 2 and 3. Taking my kitchen as an example: Area: 12.77m2 Volume 30.64m3 Using the flow rate above of 13l/s -> 46.8 m3/h, I would end up with 1.53 ACH (assuming the kitchen itself was balanced, either by equal number of supply/extracts or by a suitable door undercut). However a house built to the exact same airtightness and thermal specs with a kitchen double the size, would end up with half the ACH figure. Clearly this is cannot be right, can it? What's more, for my very small ensuite I would end up with just over 4 ACH - practically a clean room! Just for fun, I tried a different method: Requirement 1 states whole house flow rate of minimum 0.3 l/(s.m2), that is 1.08 m3/(h.m2). Say I want to design for double this flow rate for the kitchen, that is 2.16 m3/(h.m2). For kitchen area area and volume stated above, this leads to 55.14 m3/h, or 0.9 ACH. Importantly, this method would give equal performance no matter the size of the room. Now, applied to the whole house: Requirements 2 and 3 give a total flow rate for the house of 306m3/h. Requirement 1 applied to the whole house gives 105m3/h. Using the alternative method with 2x multiplier for kitchen, 1.5x multiplier for bathrooms, 0.8x multiplier for all other rooms (where the (arbitrary) multiplier is applied to the whole house flow rate 0.3 l/(s.m2)), I get a total flow rate of 124.86 m3/h. Requirement 1 applied to the whole house obviously still is 105m3/h. So, how do I make of this? Spreadsheet is attached for your perusal, if you wish. 20240220 - ventilation_calcs.xlsx

@JohnMo: an Italian told off by (presumed) British for using British Thermal Units - hilarious 🤣 Joking aside, many thanks for link, I’ll have a read. Assuming your guess is correct, 10mm is still not my favourite in terms of how it looks but I could just put a decent sleeve on it and reroute so that it disappears neatly into the wall. It still leaves the problem of a 22mm pipe in a notch which is really too small for it though. If keeping the loop, how about replacing the 22mm with two 15mm next to each other where it crosses joists? In practice I would replace all the runs along west and east elevations. @OwenF Many thanks for sharing. I already have a 200-W and a new cylinder so I would like to make the best of it now. I ruled out UFH upstairs because the joists are not hung to blocks but rather built into them and not sealed so I figured a good amount of it would be lost. Manifolds are an interesting route which I considered but I dislike plastic pipes, although I get that I would be using the same thing for UFH but at least is downstairs.

Apologies, I omitted that I am running the boiler in weather compensation mode without a thermostat. The boiler modulates the flow temperature based on return temperature and outside temperature. Because of this, the boiler is "always on". The larger the pipes, the lower the flow temperature can be while still delivering the required heat to the room. So far I have never exceeded 50C this winter (first winter with this boiler) but I think I could do better with larger pipes.

Hi, I am looking for some guidance on CW pipework. I have ~20-year old detached 2-floor house (91 sqm) with a heating loop in 22mm copper under the floor, which branches off to each radiator in 10mm microbore. I think the layout of the loop is per diagram below, although I have yet to take up any flooring to confirm. Boiler and DHW cylinder have been moved to the loft, roughly above the bathroom/bed2, near the gable. I indicated where heating pipes come down from the loft with red/blue squares (in the cupboard in the family bathroom). I would like to upgrade this system to 22/15mm copper. Reasons for this are: I have a new Viessmann 200-W system boiler with a very high modulation ratio. It is running hotter than necessary because of the limited flow in the small pipes The floor joists are 7 x 2. From my calculation the maximum notch depth is 175mm / 8 = 21.88mm. Builders have clearly pretended this is close enough to 22mm. In practice, pipes are noisy when heating comes on and I think this is because there's little to no space for any felt. I have seen evidence of some pipe corrosion, which I think is due to old flux left on the pipes. Several neighbours have had pinholes in the past as well. I am keen to inspect the pipework under the floor and while at it I might as well improve it. Given the above, my preference would be to run most of it in 15mm, changing from a loop + branches to a radial system, with no more than 3 rads per branch (TBD based on max BTU per branch). Questions: First of all, is my plan sensible? I would favour a layout which would allow me to do this in stages rather than all at once, so that I can tackle 1/2 rooms at a time, especially upstairs. Do you have any suggestion for the pipe layout? What is the max BTU I could put on a branch for a low temperature system? I assume this would depend on the maximum flow temperature because lower temperature means bigger radiators. These are old anyway so I wouldn't mind upgrading, if I found that was the new bottleneck. This would also be good for a future upgrade to ASHP. I would like to also move to UFH downstairs, in the kitchen and dining/living (I could live with a radiator in the hallway and cloakroom), although this work would be done later. The plan is to: First upgrade the pipes Then tackle a bathroom renovation and install the UFH manifold. I am thinking to place this to the left of the bathroom radiator, in the stud wall (green box). Bathroom radiator will also be changed to a towel rail and moved to the cupboard wall (in magenta). Is this a good location for a manifold? I would like to have it downstairs but I am struggling to find a good location for it. Finally move to UFH downstairs.

Thanks ProDave, appreciate the honesty. I think it is already priced about £50k cheaper than a similar property in good state would be but I suspect it would take more than that to restore it. This confirms my suspicion I guess.

I am considering to put an offer in for an 18th century, timber framed former dovecote, which was extended in the sixties with 2 lean-to extensions. The main part of the building is 2 floors + loft and I can clearly see it is “sliding away”, so much so that there is a substantial gap of about 2inches between one of the window frames at the ground floor and the wall. What professionals should I get involved to check what work would be required to put it right? I can add pictures if it helps. Thank you

Right, so I made a start on Structure. My intention is to go with ICF. I note that Approved Documents give guidance only on how compliance to Building Regulations can be achieved but of course there other ways, e.g. for Part A at page 6: "requirements of A1 and A2 will be met by following the recommendations given in the documents listed in Section 1 or by adopting the guidance in Section 2-4". Now, section 1 lists BS standards; section 2: A: stability B: floors and roof C: masonry walls D: chimneys E: foundations From all of that I understand that if I build with ICF section 2C does not apply (not even for the size of major openings? for max height of a building?) and I can achieve compliance by following the technical documents of a (reputable and CE/UKCA-marked) ICF manufacturer, who will comply with the relevant standards in section 1. Provided I ask for a DoC for the product that matches the listed standards, I should be ok. Is the above correct? If so, I should find in the appropriate standard a requirement for, e.g., max size of major openings, etc, which should match what section 2B states. I have no intention of buying and reading BS standards and I should trust a good SE/architect experienced with ICF builds, or shouldn't I? How do I check drawings and calcs are compliant with the standards? Thanks, Giacomo

Thanks all for the pointers. No plans yet. As I said it's very early on and I don't have a plot at the minute. Conscious of the fact it'll take a while, I would like to get ahead with some reading. I like dealing with pros when they know what they are doing and are humble. I like pros that have "the heart of a teacher" rather than of a secretive salesman but unfortunately these folks seems to be rare in all industries, including architects.

How much of the building regs would you practically recommend a newbie self builder to be familiar with? As an engineer (although electrical) I am not afraid of reading a standard and I understand that more knowledge is never a bad thing but on the other hand I don't want to waste time reading parts that I don't really need to know. Just for reference, I am very early on in the project and still looking for a plot. I would like to draft plans myself and get help from an architect only for technical drawings. I am thinking to go with ICF and do most of it myself calling in trades when required. How did you do it?

I don’t think the plot could be subdivided because there are several restrictions imposed by the council (e.g. penalties for selling sooner than a minimum number of years). Also, because it all belongs to one developer, I would think they would have subdivided before selling to maximise profit if this was a possibility. Good tip about talking to estate agents, as some properties on that estates are actually for sale so they must have done some research on that market. Thanks, Jack

Hi, New to the forum, although I have been reading for a while. My wife and I are currently based just outside Cambridge and moved to the UK about 3 years ago from Italy (both Italians). I would like to kick off with a question. How would you value a half an acre plot, reserved to self builders in a new development of ~40 properties? I know that a smaller 0.14 acre plot in the same estate has been sold for £120k and that a newly built house on a similar 0.14 acre plot is on the market for £425k (non self built). All these self build plots only have OPP. The simple answer I guess would be to scale linearly (3 times bigger plot, 3 times more expensive) but also I guess the potential value of the home built on it would be a consideration and I don’t think the value would be 3 times as much (e.g. £1.2M). Any thought from more experienced people would be much appreciated. Thanks, Jack