Is it worth putting a dehumidifier in the loft?

So you're thinking about a dehumidifier for your loft, huh? Honestly, it depends. Like, really depends on where you live, what shape your roof's in, and what mess you're actually trying to fix. A dehumidifier can totally work for moisture problems—but it's not always the smartest first move. Let's walk through what matters so you don't waste your cash.

What are the main benefits of using a dehumidifier in a loft?

The big win here is stopping condensation and that nasty mould growth. Lofts are basically terrible at breathing—they trap warm, wet air from your house below. That air hits your cold roof, turns into condensation, and boom—you've got a damp, mouldy mess. A dehumidifier pulls that moisture out, keeps humidity low, and protects your roof, insulation, and boxes of old Christmas decorations. Oh, and it'll kill those musty smells too. Air quality actually improves up there.

When is a dehumidifier NOT the right solution for a loft?

Look, a dehumidifier is often just a band-aid. It's not gonna fix a leaky roof or cracked tiles or gutters full of leaves. In those cases? You're just fighting a losing war—the thing'll run forever, suck up electricity, and do nothing real. Also, it's way less efficient than just letting the place breathe. If your loft's sealed tight and no water's getting in, a dehumidifier might be totally unnecessary. Just an ongoing expense for no reason.

What are the alternatives to a dehumidifier for loft moisture control?

Before you buy anything, try these—they're more permanent and cheaper in the long run:

• Improve Ventilation: Honestly, this is the best fix. Put in some roof vents, soffit vents, or a passive system. Air moves naturally, no electricity bills. One-time cost, done.
• Check Insulation and Vapour Barriers: Make sure your insulation's installed right and there's a vapour barrier on the warm side. Stops moisture from your house hitting the cold roof deck.
• Fix Structural Issues: Patch leaks, seal gaps around pipes and chimneys, clear those gutters. This is the most important stuff—stop moisture at the source.
• Use a Positive Input Ventilation (PIV) System: This thing pulls fresh air from outside and pushes it into the loft, replacing that stale, damp air. Way more energy-efficient than a dehumidifier for whole-loft humidity control.

What type of dehumidifier is best for a loft?

If you're sure you need one, pick the right kind. For most lofts in normal climates, a compressor (refrigerant) dehumidifier is your best bet—efficient and cheap to run. Works great in temps above 15°C, which is normal for spring, summer, autumn. But if your loft's freezing (below 10°C) or you've got a short-term damp issue, a desiccant dehumidifier handles cold better. Downside? Those cost more to run.

Key features to look for in a loft dehumidifier

• Continuous Drainage: That little tank'll fill up fast. Get one with a hose you can run to a drain or a big bucket.
• Energy Efficiency: Look for an Energy Star sticker. Keeps your bills from killing you.
• Size and Capacity: For a typical loft (20-40 square metres), a 20-pint (10L) per day unit works. Bigger space? Go 30-50 pint (15-25L).
• Automatic Humidity Control: Set it to keep 50-55% relative humidity. Stops it running when it doesn't need to.

How much does it cost to run a dehumidifier in a loft?

Depends on the unit and your electricity rates. A typical compressor uses about 300-500 watts per hour. Running 8 hours a day? That's 2.4 to 4 kWh. At average prices (say $0.13/kWh), it's roughly $0.31 to $0.52 per day, or $9 to $15 monthly. A desiccant model? That uses 600-800 watts—costs way more.

Expert Checklist: Is a loft dehumidifier right for you?

• [ ] Have you checked for and fixed any roof leaks or structural issues?
• [ ] Is your loft insulation and vapour barrier correctly installed?
• [ ] Have you maximised natural ventilation (vents, soffits, eaves)?
• [ ] Is the damp problem seasonal (e.g., winter condensation) or constant?
• [ ] Do you have a power outlet in the loft (safe, RCD-protected)?
• [ ] Are you prepared for the ongoing electricity cost?
• [ ] Can you set up continuous drainage?

If you said "No" to the first three things? A dehumidifier's just a temporary fix, not a real solution. Fix the root problem first. Seriously.

Frequently Asked Questions (FAQ)