[Strawbale] [SB-r-us] Re: Comment on forced air systems and dust

[Mark BP / Low Energy Design Ltd]

Robert Tom wrote:

>I've often wondered how people with hydronically-heated SB houses without  
>air-handling systems provide fresh ventilation air to every habitable  
>space in the house and exhaust stale and/or polluted and/or contaminated  
>air.
>

Rob -

You may find some answers in the relevant building regulations approved 
document for England and Wales, which is available at:
  
http://www.planningportal.gov.uk/england/professionals/en/4000000000339.html  
(free download)
Obviously most of the buildings to which this applies are not strawbale 
(but I don't see what difference that would make anyway).  Nearly all of 
them use circulating water as a heating medium.  (I think it's fair to 
say that the general view of blown air systems among those Brits who 
have experienced them is that they are cheap and nasty, they don't meet 
peoples' real thermal comfort requirements, and they create a lot of 
intrusive noise.  Fwiw, this is a view which I still personally hold 
after 2.5 years living in a Canadian house with blown air heating.  
Anyway my point is that Brits generally don't use blown air systems in 
dwellings unless they have no other option.)

Admittedly the relevance of much of the advice therein is 
climate-dependent.  In most British buildings, if you do your 
ventilation design to take care of condensation risk then you've already 
taken care of contaminants (except in WCs).  And a windy climate usually 
makes passive ventilation (or the passive component of an overall 
ventilation strategy) a lot easier.  Even so, the most common British 
strategy (System 1 on page 11 of the document) of humidistat-controlled 
fans extracting from "wet" rooms and adjustable slot vents in "dry" 
rooms could probably be applied more widely.

Though it's not the way I'm heading in my own thinking at present.  For 
near-net-zero housing, at least in a heating climate, the Passivhaus 
approach of dedicated and carefully controlled [low flow rate] 
ventilation for each space makes a lot of sense.  But that presupposes a 
desire to do away with the need for space heating for all but a few days 
per year.

Mark