To all those suggesting a larger 2-stage HP to provide 100% heating without back-up and NOT be oversized for cooling. Yes this will work to cover the difference between a GSHP providing 95% of the seasonal heat and that last 5% - but at what cost?
A larger, more expensive HP and what else?
A larger ground loop (more drilling!), maybe a second circulating pump – there goes your monetary efficiency (longer payback), and for what, a few days a year?
It’s your money…
More CO MI$$IONfor a much more expensive system.
It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities