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Viewing 15 posts - 526 through 540 (of 983 total)
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  • Nick Grant
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      Paul

      First work out what the heat loss is.

      Do you have timber going through the internal wall to outside wall? Would be more of a concern for me because of damp/rot issue. Wall is just an energy loss and condensation risk.

      Nick

      Nick Grant
      Participant

        Agree useful if applied accross whole building.

        Nick Grant
        Participant

          Nice Therm work Mark but I'm not sure how usefull % degredation of U value is as a concept as U values are area based and psi are linear. Paul needs to work out the heat loss through the walls and add the length x psi heat loss.

          This is easy in PHPP but can do long hand for SAP I assume.

          Nick

          in reply to: Re: Re: solar air heater in passive house #35563
          Nick Grant
          Participant

            Perhaps it is the recent weather but I've been having similar thoughts.

            In the past such ideas probably failed because the building heat loss was so high despite foot thick insuation but now we are learning to plug the heat leaks perhaps there is a role.

            Dave, whilst such an air heater could work East and West it is worth noting that as well as overheating, E and W windows will result in a net loss of useful heat. At least according to my PHPP modeling. Just need them for views or daylight.

            Nick

            Nick Grant
            Participant

              Rod

              I'll chip in what little I know.

              As Dave says it is usual to use the rough opening. Putting insulation over the frame will reduce the installation psi value, indeed if you are using solid wood frames you can get a negative psi value. If the frames are insulated already then the effect of the external insulation is less dramatic as seen in the examples in the manual.

              What you will find is that you will probably struggle to get as much insulation over the lower frame by the cill so will end up with different psi values for this. There is an unclear instruction in the manual about this. The trick is to set the installation psi to 1 in the window description then put the psi values in the window worksheet instead of 1s when a side is in contact with a wall rather than another frame.

              Do hope that helps.

              Nick

              in reply to: Passive House is Childs Play #34293
              Nick Grant
              Participant

                It is great to see a kid's book being discussed in such technical detail!! Fantastic.

                Technically way ahead of so many books intended for adults.

                However it seems that in the UK climate the energy benefit from earth tubes or brine loops is very modest indeed, although I'm not sure if we have a good handle on the electricity saved from defrost in the MVHR.

                Thanks for your input to the forum Martina, I hope the book sells widely.

                Nick

                in reply to: The PHPP and ‘natural’ materials? #35536
                Nick Grant
                Participant

                  Hi Matt

                  Mark's summary is correct.

                  PHPP is a building energy model, you can use whatever materials you like, as long as they work and you know the U value of the proposed construction.

                  For moisture modelling you can either design out the problem or where this is not possible (eg renovation or old buildings) then software such as WUFI can be used. However with all software garbage in garbage out. It is always necessary to make simplifying assumptions and that is part of where the skill lies.

                  As usual I have to disagree with Tom.

                  For me the real beauty of a 'simple' spreadsheet type model such as PHPP is that you can see where the numbers come from, it is physics, you can look under the hood.

                  As it happens, PHPP shows that the steady state model is surprisingly good especially once you get to low energy use so temperature swings are minimised. In terms of computing power I'd give my money to a good building physicist with a calculator from the pound shop any day.

                  IMHO fancy front ends and cad integration can hide all manner of assumptions.

                  Designing low energy buildings requires a deep understanding of basic principles. No amount of software will do the job for you any more than an electronic guitar tuner will help you play jazz, as I have discovered to my bitter disappointment.

                  On the ventilation front PHPP will let you model a lower ventilation rate if you believe that nasties will be magiced away through the walls but see else where for discussion of air-tightness, breathability and ventilation. However the PHPP default is already lower than typically used for small UK homes.

                  Nick

                  in reply to: Re: Re: Cedar Cladding #35530
                  Nick Grant
                  Participant

                    I will check with Webmaster re autoscaling but simplest solution is to post smaller photos unless the detail is required.

                    I only know Macs which allow pics to be saved for web or email or can use Photoshop Elements to save for web quickly setting size (pixels) and quality.

                    Autocompression could loose some subtle detail that might matter for some pics and not others.

                    I have changed Neil's pic.

                    in reply to: Weather data for PHPP #35294
                    Nick Grant
                    Participant

                      You are right about the peak heating load Mark but data should be fine for monthly heat load method.

                      Anyone know if the €50 Meteonorm data can be pasted into PHPP?

                      Nick

                      Nick Grant
                      Participant

                        Drainage wise I'd be happier with some sort of drained 'moat' and drawbridge although I realise that conjures up the wrong image. Say 150 – 200 deep with ramp/grille over at door or all round to suit look.

                        Slab could be a little higher than the ground beyond the moat if ramp has gentle slope.

                        Filling the moat with stone introduces splash problem and it could block over time and then fail is weather like we are having at the moment.

                        Must say I was thinking damp and heat loss not wheelchairs when I designed our place with slab 300mm above ground level, not good.

                        Nick

                        in reply to: Re: Re: Finding A++ appliances #34428
                        Nick Grant
                        Participant

                          Think I will need to pick my moment before suggesting this procedure to Sheila.

                          in reply to: Weather data for PHPP #35292
                          Nick Grant
                          Participant

                            Given the variation in weather for any given location (in the UK especially!) I'm of the uninformed opinion that we need representative weather data rather than fine grained very location specific data.

                            As I see it the weather data will influence various aspects of design through PHPP (or other model).

                            eg if it is a cold and sunny climate then more South glazing could be a benefit but if it is a cold and cloudy climate with regular freezing fog then smaller windows could be a benefit. Similar issues when balancing overheating.

                            ie it is the aspects of the weather data that influence the building format, glazing ratios etc that matter more than the data that sets the exact insulation thickness to meet a nominal 15kWh/m2. We know that adding insulation will reduce heat loss (at a cost) but reducing glazing area (South) might increase or reduce heating depending on climate.

                            IMHO this sort of variation is more important than say exact degree days in isolation. If we feel that our project is in a location that is 'less mild' than available weather files we can always up the design temperature so that our design is conservative.

                            What I don't know is how many weather files we would need to reasonably describe the UK or how we would choose the relevant file given that we have weather rather than climate.

                            The alternative is to produce a weather file for your specific location using Meteonorm but I have no idea how to do that! http://www.meteonorm.com. They offer data sets for a reasonable €50 but I don't know if these are in a form that can be pasted into PHPP. Certainly I heard at the PH conference that Meteonorm can produce output for PHPP.

                            As discussed elsewhere PHPP uses temperature and solar data to determine heat demand but needs different data generated by PHI using a dynamic model to estimate peak heat load requirement (important if heating with ventilation air only or using air source heat pump).

                            Whilst some sort of generic algorithm may never happen the immediate opportunity/problem is how to avoid many individuals having to pay for the same data several times.

                            Might be something that could happen via the AECB/CLP.

                            Anyone out there with experience of putting weather data into PHPP?

                            Nick

                            Nick Grant
                            Participant

                              Steve

                              Thinking about your detail again, do you have any trouble fixing to the slab at the edge?

                              I'm thinking the bricks are not ideal for fixing and the slab will be some way in assuming a reasonable thickness of insulation.

                              Alternative is shuttering (a pain I know) to support the edge insulation as you pour the slab.

                              Nick

                              Nick Grant
                              Participant

                                Hi Steve

                                No not worried about the XPS crushing (we have no thermalite or other support under our un-edge-thickened slab), more that if edge is more rigid than middle I would have expected a possible problem with settlement. Question for the engineer, depends on loads and spans of course. My point is that same detail required to reduce thermal bridge.

                                Generally loads from dividing walls etc help un-bend the lab.

                                Guess what I'm thinking is that if support needed at edges then probably under other loads as well.

                                Preference being insulation all round.

                                Like your brick shuttering, obviously need insulation over this on outside which I think you said before.

                                Nick

                                in reply to: Airtightness Vs Breathability #35394
                                Nick Grant
                                Participant

                                  Hi Paul

                                  Sorry not to be clear but I was not suggesting 50 Pa too much for a blower door test only that this is quite a pressure yet still lower than the vapour pressure quoted. ie under normal conditions the differential between vapour and air pressure will be even greater.

                                  BTW for Passivhaus both a suck and blow test is done but vents are sealed up with sticky film.

                                  However I'm still confused by vapour pressure which I never really grasped first time round at Uni. Your explanations however help, really appreciate your input on the forum, thanks.

                                  Cheers

                                  Nick

                                Viewing 15 posts - 526 through 540 (of 983 total)