OpenHeatLoss - Free and Open source heat loss, system and pipe sizing tool, primarily for heat pump system design

[SimonD]

10 hours ago, marshian said:

Makes perfect sense - before I insulated between the joists of the ground floor with 75mm PIR you could feel a draft in most rooms when the wind got up - now it can be a bloody good gale outside and there is no drafts at all........ I know I've got the house reasonably well sealed hence the installation of a PIV unit to manage humidity and ACH's (But it's not MVHR  )

 

That is the answer to the ventilation anomaly. The reduced method by CIBSE only accounts for naturally ventilated (with extract fans etc.) or continuous MVHR, not for unbalanced whole house situations such as PIV or MEV. In these cases the full BS EN 12831:2017 method needs to be applied - hence coming soon to the tool. There are a couple of notes in the app, but I don't think this is clear enough at the beginning where the initial Ventilation and Air Permeability settings are input - so I will make sure it's clearer and explained properly for users. There's also a drop down at the bottom of the room editor to select continuous mechanical ventilation and if unbalanced is selected there is a note to say it is outside the current method scope. Again, something natural for me as the designer, I therefore easily overlook it as not that sensible for a user! Thanks. 

[marshian]

1 hour ago, SimonD said:

 

That is the answer to the ventilation anomaly. The reduced method by CIBSE only accounts for naturally ventilated (with extract fans etc.) or continuous MVHR, not for unbalanced whole house situations such as PIV or MEV. In these cases the full BS EN 12831:2017 method needs to be applied - hence coming soon to the tool. There are a couple of notes in the app, but I don't think this is clear enough at the beginning where the initial Ventilation and Air Permeability settings are input - so I will make sure it's clearer and explained properly for users. There's also a drop down at the bottom of the room editor to select continuous mechanical ventilation and if unbalanced is selected there is a note to say it is outside the current method scope. Again, something natural for me as the designer, I therefore easily overlook it as not that sensible for a user! Thanks. 

 

Thanks

 

Probably a good time to provide a review

 

In summary - I found the "Open Heat Loss" tool easy to use (The dt element between rooms/external areas probably needs a bit more notation to explain what it's trying to achieve from a "non heating engineer" perspective - clearly you had an excellent understanding of it and could fix my schoolboy errors)

 

I completed the whole house heat loss over two evenings - maybe 2 hrs each day

 

I did however have

 

1. All the dimensions of floors, walls, windows and doors in a handy table

2. All the U values for the fabric elements of the house noted down

 

Both the above from a previous heat loss exercise which made data entry quite quick and easy

 

It works on phone (if a little scrolly) Android tablet and PC 

 

The various report pdfs are great as a summary snapshot

 

I need to go back to my pipe work section and revisit that as I took a punt on lengths I effectively have two circuits linked together just after the pump

 

If I was to suggest anything it would be - from a room to dT perspective it would be good to link ground floor to upstairs (In my mind I have a "room above" or "room below" selection process) how feasible that would be I don't know