Technical blog
Analyses, methods, and best practices in HVAC energy efficiency, by the M-itech engineering team.
Accounting for HVAC Equipment in an Energy Audit: Method, Pitfalls and Shortcuts
In an energy audit, the HVAC line is often the heaviest and the least well documented. Here is what an audit expects from an HVAC unit, how to establish its baseline consumption and quantify a replacement measure, and how to get those figures out faster.
Read the articleVRF or two-stage compressor: what two real COP curves reveal
Two rooftop heat pumps of comparable capacity (~15 tons), two compressor technologies: VRF modulation or two fixed stages. We overlaid their COP curves taken from real datasheets. The gap shows up in heating, below freezing, exactly where a Quebec winter hurts.
Read the articleQuick Payback Analysis or Full Energy Simulation: Which Tool for Which Job?
Quick payback analysis and detailed energy simulation answer different questions. Here is how to pick the right tool for the project, without pitting the two approaches against each other.
Read the articleConverting a Gas Rooftop Unit to a Heat Pump: What to Evaluate Before Deciding
Replacing a natural gas rooftop unit with a heat pump is a decision worth preparing. Here are the factors to weigh (climate, energy costs, electrical service, winter peak) before choosing between gas, full conversion or dual-energy.
Read the articleRepair, Replace or Retrofit: How to Decide
Choosing whether to repair, replace or retrofit an HVAC asset is a strategic decision, not just a technical one. Here is how to structure the call before an emergency makes it for you.
Read the articleWhy Excel reaches its limits for asset management
Find out why Excel spreadsheets become risky for building asset management, and which approaches lead to better investment decisions.
Read the articleA make-up air unit's R-value: real efficiency lever, or brochure talking point?
Does better wall insulation on a make-up air unit actually improve its energy efficiency? It depends on one thing that's often overlooked: where the heat is produced inside the unit.
Read the articleDefrost: the blind spot in heat-pump ratings
Defrost is real, large, and specific to each machine, yet ratings (AHRI 210/240, HSPF/HSPF2) dilute it and most calculations ignore it or flat-rate it. Here is why it's the blind spot of winter performance, and how Optima estimates it more accurately, hour by hour.
Read the articleThe 17/47 trap: why two numbers can't predict a heat pump in a Quebec winter
Heat pumps are rated at 47°F and 17°F. But real performance is a curve, not a straight line between two points. Here is why trusting 17/47 skews your savings and payback calculations, and what changes when you analyze the real curve.
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