yes and so you should think about the long term, thats why the archs on this forum bang on about construction drawings and taking the time to plan the ventilation layouts at as earlier a stage as possible, preferable before going to site..
re manky pipes - you install smooth bore rigid pipes and grills/terminals etc (arranged for future access to allow for cleaning)
there will be components in the MVHR unit to be changed, so above that's why i recommend the larger European manufacturers that have been around for yonks and will be around at that this future replacement stage.
so think about your pipe runs, have you allowed adequate space? can the main legs be arranged in a storage press for instance to allow for future maintenance etc... can the unit be within the thermal envolpe and so on
if your not bothered with mvhr, before your move forward consider my question above. calculate how much it will cost to heat your building from say 0degs to 20degs and keep it there for a 24 hour period then ask yourself what your expected air-changes per hour will be? the current regs stipulates a pass rate of 7 air changes per hour. will you get to 3,2,1, passive levels? and if you got to say 2ACH how much better would it be if you were recycling say 70% of that heat? and how long would it take to pay back your initial investment?
i wish you well with whatever you decide, but please come back and let us know how your getting on. seriously, a bit of data feedback on mvhr and dcmev systems would be welcome