Edited; I have only read testing reports and wired abatement pumps. I modified my answer based on the feedback. As I have said in other posts granite especially pink or rose can be a significant source of radon.
I would not run the system while you are away, I probably would open the house lower level windows or vents when you arrive. You may even want to ...
The soffits need to be cleared of their insulation. Otherwise you risk having mold forming due to the humidity not being able to get out.
There should be vent baffles installed to allow the air to continue to flow over the insulation.
You may have an HVAC contractor install additional events to push more air into the area.
Try a couple of appropriately-sized cardboard boxes find some of decent quality that will hold up fill them with those air pocket shipping things tape or four-way them shut. Make two or three of these per unit then take them out and put them back in as space is needed usually it's better not to let things run for long periods of time with no load. Not only ...
Since tenants are involved, you'll need to do this right
If you were owner-occupying a zoned single-family dwelling, then taking shortcuts in the interest of expediency would be an acceptable way to get rough estimates of zone energy usage for your own uses. However, you're not in that situation; you're dealing with tenants instead, which brings real ...
No, that's not a valid way to determine energy usage. With a hot water system you need to know three things:
The flow rate of the water
The temperature drop of the water through the loop
The time over which this happens
With these 3 you can determine the energy "lost" in the loop which presumably went into your rooms.
The "magic" formula you'll need is:
It might be dangerous to assume that each pump delivers the same flow to each zone so you may need more than the run-time for an accurate set of results.
So pump run time, flow rate and the temperature drop of the fluid delivering the heat (ie supply and return temperature).
You could then compare with the boiler hot water output using the run-time of the ...