Heatloss Calc's, a different way?

Hilly

Maybe I am being overly simplistic so please feel free to set me straight.
1) Heat source for the home is turned off.
a) Every room in the house would receive a sensor to monitor and record the temperature.
b) There would be sensors placed outdoors to monitor and record temperature.

So know you have your indoor and outdoor temperature for a given period of time. I'm sure software could easily be designed to do the math and tell use what the actually heatloss is in the building. Am I being to simple with this thought? We could easily turn off a heat source in a shoulder season for long enough to get an accurate number. Then simple mathematics could help adjust that number to the areas DDT. Just a thought... maybe I'm way of the mark.

STEVEusaPA

I floated a similar idea about 5 years ago. Get an actual real time heat loss would save lots of time calculating. Of course the variables-solar gain, etc. would play into it, but overall I think it would have to be more accurate:
https://forum.heatinghelp.com/discussion/140670/actual-heat-loss-vs-calculated-heat-loss#latest

Jamie Hall

Nothing wrong with the concept. Nor with another approach to measuring heat loss in an existing structure -- measuring the energy used to maintain temperature (allowing, of course, for boiler or whatever efficiency).

And in a sense this type of approach is, perhaps, more accurate. Trouble is, there are many many other variables -- @STEVEusaPA mentions solar gain, but there is also wind, and preexisting state of the building, and a a host of others.

The other problem, of course, is that it doesn't help much for dealing with either new construction or building renovation.

EBEBRATT-Ed

Won't work.

Heat loss is based on temperature difference, wind, infiltration etc. Internal heat gain from people, appliances, lighting etc is not considered. The vacant building has the highest heat loss but when unoccupied is kept at a lower temperature.

Heat gain is the opposite, temperature difference, wind , infiltration but then if you don't consider, internal heat gain (appliances, computers. lighting), people, humidity, solar gain and building mass (the time it takes for heat to soak through a buildings roof and wall structure) you would be screwed.

So TD is only one small piece of the puzzle

Hilly

If the home is lived in and the heat source is off wouldn't it actually be a realistic number? Again maybe I am being to 1 dimensional in my thinking about it.

I know there are variables that change from day to day but paper calculations can be just as unpredictable. Picking an infiltration rate on an existing house is almost like throwing darts at board blindfolded. houses in my parents neighbourhood where built in the late 70's and early 80's. Rumour is the contractor was known for having an inspection and then taking all the insulation and installing in next door for the next inspection days or weeks later. Literally there were houses found without insulation.

Harvey Ramer

Here's what I would like, and it could easily be done. Every comfort appliance should come with an indoor and outdoor sensor. It should then log the daily energy consumption along with the corresponding TD. This could be used by the appliance to predict required energy input and make adjustments in real time based on indoor and outdoor feedback.
After the first generation of equipment, replacement installers could look at the digital logs and make an accurate determination on required appliance capacity, in minutes.
It would also allow technicians to view system efficiency degradation over the a period of years.

I realize that TD is not everything, however, collected over a period of years, it would prove to be an invaluable tool, if properly applied.

Solid_Fuel_Man

I'm thinking of a field applied btu meter. Something of an ultrasonic flow meter that could be put on a boiler's supply or return and two temp sensors. This would account for total heat that a radiation system is actually supplying. The only miscalculated data would be radiation from the boiler itself. You could do the same thing with FHA as well, just monitor velocity of the air in the supply plenum.

You could then collect data of OAT, to correspond with total btu requirements of the structure. Similar to what Harvey is talking about, but something a tech could apply and generate a data log of over several weeks/months before sizing new equipment.