STEP BY STEP: The beauty of internal spaces

Step by Step is the blog of Kate Kerin Interiors. In addition to following some of my clients’ projects, I examine some of the latest issues of interest in the world of interior design.

Designing with Darkness: Making the Most of Internal Rooms

Every so often, I work on a project that includes an internal or even subterranean room—spaces without natural light or direct ventilation. One of my clients recently had just such a room, tucked deep within the floor plan, with no windows at all. At first glance, this type of space can feel uninspiring or even unusable. But with the right approach, these rooms can become some of the most interesting and versatile in the home.

My clients Melissa and Grant have a four-level terrace home in Sydney’s harbourside suburb of Birchgrove. In a tucked-away corner of their home, a space with a natural sandstone wall has been embraced as a potential music listening space for Grant. There are no windows, and the floor is exposed cement. There’s a little nook that has no obvious purpose, and the ceiling is low. I can’t wait to get my hands on this space to turn it into Grant’s perfect den – leaning in to a Manhattan vibe, with lush velvets, bold colour, metallic wallpaper on the ceiling and warm colours. This is my go-to internal space, which I’m convinced is going to be the favoured room for the whole house.

In this blog, I’ll explore the benefits and drawbacks of windowless spaces, and how clever design can transform them into beautiful, comfortable and practical rooms.

Grant’s music room will have bold colours and lean into the internal aspects of the space.

The Benefits of Internal Rooms

It’s easy to think of a lack of windows as purely negative, but internal rooms can actually offer some unique advantages. Because they’re not exposed to the outside world, they tend to be naturally private and cocoon-like. That makes them perfect for spaces where you might want to retreat from the bustle of daily life. A quiet study, a library or a media room can thrive in this environment, where distractions from traffic, neighbours or passing light are absent.

Another benefit is temperature stability. Without windows, these rooms don’t suffer from draughts, baking western sun or frosty winter mornings. They hold a more consistent temperature, which is ideal for spaces like wine cellars, gyms or entertainment rooms where comfort and climate control are essential.

From a design perspective, internal rooms can also feel liberating. You’re not constrained by window placement, views, or daylight. Instead, you have a blank canvas where lighting, colour and finishes can be used boldly. Deep, moody tones or dramatic wallpapers that might overwhelm a sun-filled living room can feel perfectly balanced in a windowless space.

The Drawbacks

Of course there are limitations. Human beings are naturally drawn to daylight, and in its absence a room can quickly feel heavy or claustrophobic. Without natural ventilation, stale air can also be a problem if the room is not properly serviced by air conditioning or extraction.

Value is another consideration. In real estate, a room without a window often cannot legally be described as a bedroom, and it may therefore be seen as “lesser” unless the design elevates it. An internal room presented as a dumping ground or storage closet can devalue a property, while the same space thoughtfully designed as a home office or media retreat can feel like an asset.

Perhaps the greatest risk, though, is monotony. With no changing light or outdoor views, internal rooms require layers of visual and tactile interest to avoid feeling flat or dull. Without that, they can end up as the least used room in the home. Grant’s internal room is really just four walls and a ceiling – broken up by some lovely sandstone features that we will retain and celebrate.

Leaning Into Darkness

The most successful approach is not to fight the absence of light, but to embrace it. Internal rooms often come into their own when designed as intimate, atmospheric spaces. Rather than trying to mimic a bright sunlit room, I recommend you lean into the moodiness.

A rich, dark palette can feel enveloping rather than oppressive. Deep blues, velvety greens or even a luxurious charcoal create a sense of sophistication that works especially well in spaces like media rooms, wine cellars or snug reading rooms. Combined with soft furnishings and layered textures, these colours make the absence of daylight feel intentional, even luxurious. In my clients Melissa and Grant’s music room, we’ve chosen autumnal colours such as cinnamon, brown and copper.

Lighting becomes the star of the show in these spaces. Without sunlight dictating the mood, fittings can be used as both functional and decorative elements. Recessed LEDs or dimmable ceiling fixtures provide general light, while sconces, lamps or uplighting can be used to highlight art, joinery or architectural detail. In some cases, lighting systems that mimic the natural shifts of daylight can help regulate mood and body rhythms, making the space feel more connected to the outside world.

Bringing Life Through Texture and Detail

With no views to draw the eye, everything within the room itself carries more weight. That means texture, pattern and detail become crucial. A velvet sofa, a wool rug underfoot, or a timber wall panel can all add layers of comfort and richness. Wallpaper can also be transformative—bold patterns or subtle metallics catch the light and create movement in a way that flat paint cannot. Grant’s sandstone fire surround adds warmth and texture to his music listening room and we’ll put a gold and chocolate brown wallpaper on the ceiling.

Artwork is another powerful tool. An internal room is the perfect gallery space, free from glare or fading sunlight. Large canvases or carefully curated collections can give personality and interest, helping the room feel purposeful rather than leftover. Mirrors, too, can add depth and a suggestion of light, expanding the sense of space. In Grant’s room we’ll add hand-painted vinyl album racks where he will rotate an ever-changing collection of his album covers, cleverly disguised as art.

Comfort and Ventilation

Without windows, comfort depends on mechanical solutions. Good air conditioning and, where appropriate, extraction are non-negotiable. For spaces with heavy use—such as gyms or media rooms filled with electronics—circulation is key to keeping the environment healthy and pleasant. Ceiling fans can also be effective, moving air in a way that feels natural even in the absence of cross-breezes.

Where the floor plan allows, subtle ducting or air transfer systems can link the internal room to parts of the home that do have natural ventilation. While it won’t replicate an open window, it can provide freshness and reduce the sense of enclosure.

In Grant’s space, a metallic mesh-style curtain in a gold colour will separate the room from the rest of the house. There’s no door, but this screen will allow airflow while also encouraging privacy and coziness.

Dark, indoor spaces can be moody and elegant.

From Forgotten Corner to Favourite Room

What’s most exciting about internal rooms is their potential for transformation. When thoughtfully designed, they can become some of the most memorable spaces in a home. I’ve seen clients turn these rooms into cinematic home theatres, luxurious wine cellars with tasting tables, serene yoga studios or beautifully appointed guest suites. Each project is different, but the common thread is that the room is given a clear purpose and a carefully considered design.

An internal room may never have the same qualities as a sun-drenched living area, but it doesn’t need to. Instead, it can be something entirely different—private, atmospheric, and richly detailed.

Final Thoughts

Internal rooms, whether tucked beneath the earth or simply at the heart of a floor plan, challenge us to think differently about design. They demand creativity, intention and an embrace of mood and atmosphere. But in return, they offer privacy, intimacy and the chance to create spaces that surprise and delight.

With the right design approach, your windowless room doesn’t have to be a forgotten corner. It can be the hidden gem of your home—a place where lighting, colour and detail combine to create something truly memorable.

At Kate Kerin Interiors, I see these spaces not as problems, but as opportunities. With careful planning and thoughtful design, even the darkest room can become one of the brightest features of your home. Reach out via my website if you’d like to chat about your beautiful, exciting internal space.

Kate Kerin Interiors works with discerning Sydney clients who value quality, elegance and a seamless design experience, whether you’re downsizing, furnishing a new home or planning a major change. If you’d like to discuss your project, get in touch to book an initial consultation.

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