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New Year, New Energy Bills: How to Audit Your Home’s Performance In Winter

Winter has a way of telling the truth about your home.

If you’ve noticed faster heat loss, mould spots, higher-than-usual bills, or rooms that never seem to warm up properly, you’re not alone. The good news is: those frustrations are also useful clues. A simple winter “home performance audit” can help you understand what’s happening, prioritise upgrades, and set realistic energy goals for the year ahead.

1) Review your winter energy bills and spot patterns

Start with the evidence you already have: your bills.

What to gather

  • Your last 3-4 winter bills (or monthly statements)
  • Meter readings (if you have them)
  • Notes on anything unusual that might have been going on (cold snaps, guests staying, boiler issues)

What to look for

  • A sudden jump compared to the same period last year (even allowing for price changes)
  • A steady climb month to month that doesn’t match weather changes
  • High usage even when you were away (often points to heating controls, hot water settings, or heat loss)
  • Big differences between rooms (often shows up as “we had the heating on constantly but still felt cold”)

Quick self-check questions

  • Does the heating run longer than usual to feel comfortable?
  • Are some rooms warm while others stay cold?
  • Do you rely on portable heaters more than you expect?

If the answer is “yes” to any of these, it’s worth doing the DIY checks below.

2) DIY home performance checks (drafts, cold spots, condensation)

You don’t need specialist equipment to spot the most common issues. A careful walk-through on a cold day can reveal a lot.

Drafts: where heat escapes fastest

Common draft points include:

  • Around external doors (especially the bottom edge)
  • Window frames and trickle vents
  • Letterboxes
  • Attic hatches
  • Open chimneys
  • Pipe penetrations under sinks and behind appliances

DIY tip: On a windy day, hold a tissue near suspected gaps. If it moves, you’ve found a draft.

Cold spots: signs of poor insulation or thermal bridging

Cold spots often show up:

  • On external walls behind furniture
  • In corners of rooms
  • Around window reveals and door frames
  • In bedrooms over garages or porches

These areas can feel noticeably colder to the touch and may be where mould starts.

Condensation and mould: a ventilation + heat balance issue

During winter, homeowners often notice:

  • Mould spots on ceilings, corners, and behind wardrobes
  • Water droplets on windows in the morning
  • Musty smells in bedrooms or bathrooms

This usually indicates a combination of:

  • Warm, moist air (from showers, cooking, drying clothes indoors)
  • Surfaces that are too cold (due to heat loss or cold bridging)
  • Not enough ventilation (or ventilation that isn’t working properly)

DIY tip: Check extractor fans are actually extracting (hold a piece of tissue to the fan grille; it should stick lightly when the fan is on).

Uneven heat: comfort problems that point to priorities

If your home has an uneven spread of heat, it can be caused by:

  • Heat loss in certain rooms (insulation gaps)
  • Radiator sizing or balancing issues
  • Heating controls that aren’t zoned properly
  • Older systems struggling to circulate heat evenly

Make a quick list of “problem rooms” and what you notice (cold walls, drafts, damp, slow warm-up).

3) When to call in professionals for a proper assessment

DIY checks are a great start, but if you’re seeing persistent issues, a professional assessment will save time and guesswork.

Consider calling in an expert if:

  • Bills are consistently high despite “normal” heating habits
  • Mould keeps returning (especially in the same spots)
  • You’re planning upgrades and want to avoid spending money in the wrong order
  • Your home never feels warm, even with the heating on
  • You’re considering a major upgrade like insulation, heat pump, ventilation, or solar PV

A proper assessment can help identify:

  • The biggest sources of heat loss
  • Ventilation issues contributing to condensation
  • Retrofit measures that will make the biggest comfort difference first

4) Set energy goals for the year ahead (that you can actually measure)

Once you’ve reviewed bills and comfort issues, set 2–3 practical goals.

Examples:

  • Reduce heating usage by improving comfort (not by “suffering through” colder rooms)
  • Eliminate mould spots by improving ventilation and reducing cold surfaces
  • Improve comfort in specific rooms (for example, bedrooms or home office)
  • Lower bills next winter by tackling the biggest heat-loss areas first

Track one simple metric

Pick one:

  • Monthly kWh usage (if available)
  • Average indoor temperature in the coldest room
  • Number of mornings with window condensation

Small, consistent tracking makes it easier to see what’s working.

5) Use winter performance to set retrofit priorities

Winter problems usually point clearly to what should come first.

If you’re losing heat fast

Priorities often include:

  • Attic insulation
  • Wall insulation (external, internal, or cavity where suitable)
  • Draught-proofing and airtightness improvements

If you’re seeing mould and condensation

Priorities often include:

  • Ventilation improvements (especially bathrooms/kitchen)
  • Addressing cold bridges and insulation gaps
  • Heating controls that maintain steadier temperatures

If heat is uneven across the house

Priorities often include:

  • Radiator upgrades or balancing
  • Zoning and better heating controls
  • Insulation upgrades in the coldest rooms first

The key is sequencing: the right order of upgrades improves comfort faster and helps every measure perform better.

Ready to improve comfort (and bills) next winter?

If winter exposes issues like fast heat loss, mould spots, higher bills, or uneven warmth, now is the perfect time to act.

Leetherm can help you assess what’s really happening in your home, identify the best next steps, and plan upgrades in the right order – so you get a warmer, healthier home and better value from every improvement.

Leetherm is a SEAI-registered One Stop Shop, which means we are fully up to date on the latest grants and supports available to help homeowners offset the cost of home energy upgrades. We manage the process end-to-end – from assessment and planning through to project delivery and grant administration – so you can move forward with confidence and clarity. And we’ve helped hundreds of homeowners just like you create a healthier, cosier, more energy-efficient home, with upgrades that are prioritised properly and built to last. Get in touch today by filling out our enquiry form, and one of our local energy experts will be in touch to talk through your home, your goals, and the best next step.